WorldWideScience

Sample records for modeling regional seismic

  1. Seismicity acceleration model and its application to several earthquake regions in China

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    With the theory of subcritical crack growth, we can deduce the fundamental equation of regional seismicity acceleration model. Applying this model to intraplate earthquake regions, we select three earthquake subplates: North China Subplate, Chuan-Dian Block and Xinjiang Subplate, and divide the three subplates into seven researched regions by the difference of seismicity and tectonic conditions. With the modified equation given by Sornette and Sammis (1995), we analysis the seismicity of each region. To those strong earthquakes already occurred in these region, the model can give close fitting of magnitude and occurrence time, and the result in this article indicates that the seismicity acceleration model can also be used for describing the seismicity of intraplate. In the article, we give the magnitude and occurrence time of possible strong earthquakes in Shanxi, Ordos, Bole-Tuokexun, Ayinke-Wuqia earthquake regions. In the same subplate or block, the earthquake periods for each earthquake region are similar in time interval. The constant αin model can be used to describe the intensity of regional seismicity, and for the Chinese Mainland, α is 0.4 generally. To the seismicity in Taiwan and other regions with complex tectonic conditions, the model does not fit well at present.

  2. A model of characteristic earthquakes and its implications for regional seismicity

    DEFF Research Database (Denmark)

    López-Ruiz, R.; Vázquez-Prada, M.; Pacheco, A.F.;

    2004-01-01

    Regional seismicity (i.e. that averaged over large enough areas over long enough periods of time) has a size-frequency relationship, the Gutenberg-Richter law, which differs from that found for some seismic faults, the Characteristic Earthquake relationship. But all seismicity comes in the end from...... active faults, so the question arises of how one seismicity pattern could emerge from the other. The recently introduced Minimalist Model of Vázquez-Prada et al. of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault. Here, we show...... that a Characteristic Earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region. The resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non-characteristic events triggered in the faults...

  3. High-Resolution Seismic Velocity and Attenuation Models of the Caucasus-Caspian Region

    Science.gov (United States)

    2010-03-20

    bottom). complicated tectonics . Lg appears to propagate well in the Arabian plate but is dramatically attenuated in the Lesser Caucasus. This may be...AFRL-RV-HA-TR-2010-1022 High-Resolution Seismic Velocity and Attenuation Models of the Caucasus-Caspian Region Robert J. Mellors...Resolution Seismic Velocity and Attenuation Models of the Caucasus-Caspian Region 5a. CONTRACT NUMBER FA8718-07-C-0007 5b. GRANT NUMBER 5c

  4. Modeling Regional Seismic Waves from Underground Nuclear Explosion

    Science.gov (United States)

    1989-05-15

    applications to modeling NTS seismograms, Pure AppL Geophys. (in press). Thatcher, W. and R. M. Hamilton (1973). Aftershocks and source...seismograms. J. Pure and Appl . Geophys., 128, 101-193. Stevens, J. L. and S. M. Day (1985). The physical basis of m6 , Ms and variable frequency magnitude...the far-field rise time for P and S are given by 7V- Ral and 72m-RD/P rspectively. The time historia of cpluio s are nsully =prumed in tarus of

  5. Flat vs. Normal subduction, Central Chile: insights from regional seismic tomography and rock type modeling

    Science.gov (United States)

    Marot, Marianne; Monfret, Tony; Gerbault, Muriel; Nolet, Guust; Ranalli, Giorgio; Pardo, Mario

    2013-04-01

    The Central Chilean subduction zone (27-35°S) is host to a multitude of unexplained phenomena, all likely linked to one another. Here, the 35 Ma oceanic Nazca plate is subducting beneath South America with a well developed, highly seismic flat slab, very well correlated with the subducting Juan Fernandez seamount Ridge (JFR) track, and also with the absence of volcanism at the surface. The upper plate, currently under compression, is composed of a series of accreted terranes of various origins and ages. Although no general consensus on the formation of this flat slab has been yet achieved, there may have been influence of overthickened oceanic crust, delayed eclogitization and consequent fluid retain within the slab, and slab suction due to the high convergence rate with the thick Rio de Plata craton. Therefore, the main questions we address are: Does the slab dehydrate along the flat subducting segment? If so, how hydrated is the slab, at what depth does slab dehydration occur, where are the fluids transported to, and where are they stored? Is magmatism still active beneath the now inactive arc? Are accreted terranes and suture zones important attributes of this subduction zone? Do they possess their own mantle entities? To answer these questions, we analyzed recorded local seismicity and performed regional 3D seismic tomography for Vp and Vs. Combining seismic tomography with 2D instantaneous thermo-mechanical modeling for the regions of flat and normal subduction, we predict rock compositions for these two regions based on published mineral and rock elastic properties. Here, we present a comparison between the normal subduction zone to the south, reflecting typical and expected features, and the flat slab region to the north, exhibiting heterogeneities. Our results agree with other studies for a dry and cold continental mantle above the flat slab. We distinguish the Cuyania terrane with overthickened crust and/or abnormal mantle beneath it. We notice that the

  6. Near-Field Probabilistic Seismic Hazard Analysis of Metropolitan Tehran Using Region-Specific Directivity Models

    Science.gov (United States)

    Yazdani, Azad; Nicknam, Ahmad; Dadras, Ehsan Yousefi; Eftekhari, Seyed Nasrollah

    2017-01-01

    Ground motions are affected by directivity effects at near-fault regions which result in low-frequency cycle pulses at the beginning of the velocity time history. The directivity features of near-fault ground motions can lead to significant increase in the risk of earthquake-induced damage on engineering structures. The ordinary probabilistic seismic hazard analysis (PSHA) does not take into account such effects; recent studies have thus proposed new frameworks to incorporate directivity effects in PSHA. The objective of this study is to develop the seismic hazard mapping of Tehran City according to near-fault PSHA procedure for different return periods. To this end, the directivity models required in the modified PSHA were developed based on a database of the simulated ground motions. The simulated database was used in this study because there are no recorded near-fault data in the region to derive purely empirically based pulse prediction models. The results show that the directivity effects can significantly affect the estimate of regional seismic hazard.

  7. The seismicity research in the sub-regions of Chinese mainland using strain accumulating and releasing model

    Institute of Scientific and Technical Information of China (English)

    马宏生; 刘杰; 张国民; 李丽

    2002-01-01

    The sub-regions are divided for the seismicity of the Chinese mainland based on the hypothesis of the active crustal blocks and the division of the active boundaries. On this result, the seismicity of each active crustal blocks are studied by calculating the accumulated and released strain of the earthquakes based on strain accumulating and releasing model, and the different seismicity stages of the sub-regions are discussed basically. Finally we have discussed the premise of the model application and the potential problems of the model results.

  8. 1-D seismic velocity model and hypocenter relocation using double difference method around West Papua region

    Science.gov (United States)

    Sabtaji, Agung; Nugraha, Andri Dian

    2015-04-01

    West Papua region has fairly high of seismicity activities due to tectonic setting and many inland faults. In addition, the region has a unique and complex tectonic conditions and this situation lead to high potency of seismic hazard in the region. The precise earthquake hypocenter location is very important, which could provide high quality of earthquake parameter information and the subsurface structure in this region to the society. We conducted 1-D P-wave velocity using earthquake data catalog from BMKG for April, 2009 up to March, 2014 around West Papua region. The obtained 1-D seismic velocity then was used as input for improving hypocenter location using double-difference method. The relocated hypocenter location shows fairly clearly the pattern of intraslab earthquake beneath New Guinea Trench (NGT). The relocated hypocenters related to the inland fault are also observed more focus in location around the fault.

  9. 1-D seismic velocity model and hypocenter relocation using double difference method around West Papua region

    Energy Technology Data Exchange (ETDEWEB)

    Sabtaji, Agung, E-mail: sabtaji.agung@gmail.com, E-mail: agung.sabtaji@bmkg.go.id [Study Program of Earth Sciences, Faculty of Earth Sciencies and Technology, Institute of Technology Bandung, Bandung 40132 (Indonesia); Indonesia’s Agency for Meteorological, Climatological and Geophysics Region V, Jayapura 1572 (Indonesia); Nugraha, Andri Dian, E-mail: nugraha@gf.itb.ac.id [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Bandung 40132 (Indonesia)

    2015-04-24

    West Papua region has fairly high of seismicity activities due to tectonic setting and many inland faults. In addition, the region has a unique and complex tectonic conditions and this situation lead to high potency of seismic hazard in the region. The precise earthquake hypocenter location is very important, which could provide high quality of earthquake parameter information and the subsurface structure in this region to the society. We conducted 1-D P-wave velocity using earthquake data catalog from BMKG for April, 2009 up to March, 2014 around West Papua region. The obtained 1-D seismic velocity then was used as input for improving hypocenter location using double-difference method. The relocated hypocenter location shows fairly clearly the pattern of intraslab earthquake beneath New Guinea Trench (NGT). The relocated hypocenters related to the inland fault are also observed more focus in location around the fault.

  10. Modelling of NW Himalayan Seismicity

    Science.gov (United States)

    Bansal, A. R.; Dimri, V. P.

    2014-12-01

    The northwest Himalaya is seismicity active region due to the collision of Indian and Eurasian plates and experienced many large earthquakes in past. A systematic analysis of seismicity is useful for seismic hazard estimation of the region. We analyzed the seismicity of northwestern Himalaya since 1980. The magnitude of completeness of the catalogue is carried out using different methods and found as 3.0. A large difference in magnitude of completeness is found using different methods and a reliable value is obtained after testing the distribution of magnitudes with time. The region is prone to large earthquake and many studied have shown that seismic activation or quiescence takes place before large earthquakes. We studied such behavior of seismicity based on Epidemic Type Aftershock Sequence (ETAS) model and found that a stationary ETAS model is more suitable for modelling the seismicity of this region. The earthquake catalogue is de-clustered using stochasting approach to study behavior of background and triggered seismicity. The triggered seismicity is found to have shallower depths as compared to the background events.

  11. LLNL Seismic Locations: Validating Improvement Through Integration of Regionalized Models and Empirical Corrections

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, C.A.; Flanagan, M.P.; Myers, S.C.; Pasyanos, M.E.; Swenson, J.L.; Hanley, W.; Ryall, F.; Dodge, D.

    2001-07-27

    The monitoring of nuclear explosions on a global basis requires accurate event locations. As an example, a typical size used for an on-site inspection search area is 1,000 square kilometers or approximately 17 km accuracy, assuming a circular area. This level of accuracy is a significant challenge for small events that are recorded using a sparse regional network. In such cases, the travel time of seismic energy is strongly affected by crustal and upper mantle heterogeneity and large biases can result. This can lead to large systematic errors in location and, more importantly, to invalid error bounds associated with location estimates. Calibration data and methods are being developed and integrated to correct for these biases. Our research over the last few years has shown that one of the most effective approaches to generate path corrections is the hybrid technique that combine both regionalized models with three-dimensional empirical travel-time corrections. We implement a rigorous and comprehensive uncertainty framework for these hybrid approaches. Qualitative and quantitative validations are presented in the form of single component consistency checks, sensitivity analysis, robustness measures, outlier testing along with end-to-end testing of confidence measures. We focus on screening and validating both empirical and model based calibrations as well as the hybrid form that combines these two types of calibration. We demonstrate that the hybrid approach very effectively calibrates both travel-time and slowness attributes for seismic location in the Middle East North Africa, and Western Eurasia (ME/NAAVE). Furthermore, it provides highly reliable uncertainty estimates. Finally, we summarize the NNSA validated data sets that have been provided to contractors in the last year.

  12. Regional Seismic Wave Propagation

    Science.gov (United States)

    1979-07-31

    Baikal to the Pamirs, earthquakes occuring in the Baikal region, Sinkiang , the Gobi desert, southwest China and the Himalayas generated Lg/P ratios...data were obtained from stations within the USSR from earthquake events occuring in Baikal, Sinkiang , the Gobi desert, Southwest China and the...earthquakes originating in the Sinkiang province and recorded by seismo- graphic stations along the Pamir-Lena River profile [25] 0 - recorded by short

  13. Southern Appalachian Regional Seismic Network

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, S.C.C.; Johnston, A.C.; Chiu, J.M. [Memphis State Univ., TN (United States). Center for Earthquake Research and Information

    1994-08-01

    The seismic activity in the southern Appalachian area was monitored by the Southern Appalachian Regional Seismic Network (SARSN) since late 1979 by the Center for Earthquake Research and Information (CERI) at Memphis State University. This network provides good spatial coverage for earthquake locations especially in east Tennessee. The level of activity concentrates more heavily in the Valley and Ridge province of eastern Tennessee, as opposed to the Blue Ridge or Inner Piedmont. The large majority of these events lie between New York - Alabama lineament and the Clingman/Ocoee lineament, magnetic anomalies produced by deep-seated basement structures. Therefore SARSN, even with its wide station spacing, has been able to define the essential first-order seismological characteristics of the Southern Appalachian seismic zone. The focal depths of the southeastern U.S. earthquakes concentrate between 8 and 16 km, occurring principally beneath the Appalachian overthrust. In cross-sectional views, the average seismicity is shallower to the east beneath the Blue Ridge and Piedmont provinces and deeper to the west beneath the Valley and Ridge and the North American craton. Results of recent focal mechanism studies by using the CERI digital earthquake catalog between October, 1986 and December, 1991, indicate that the basement of the Valley and Ridge province is under a horizontal, NE-SW compressive stress. Right-lateral strike-slip faulting on nearly north-south fault planes is preferred because it agrees with the trend of the regional magnetic anomaly pattern.

  14. Building a risk-targeted regional seismic hazard model for South-East Asia

    Science.gov (United States)

    Woessner, J.; Nyst, M.; Seyhan, E.

    2015-12-01

    The last decade has tragically shown the social and economic vulnerability of countries in South-East Asia to earthquake hazard and risk. While many disaster mitigation programs and initiatives to improve societal earthquake resilience are under way with the focus on saving lives and livelihoods, the risk management sector is challenged to develop appropriate models to cope with the economic consequences and impact on the insurance business. We present the source model and ground motions model components suitable for a South-East Asia earthquake risk model covering Indonesia, Malaysia, the Philippines and Indochine countries. The source model builds upon refined modelling approaches to characterize 1) seismic activity from geologic and geodetic data on crustal faults and 2) along the interface of subduction zones and within the slabs and 3) earthquakes not occurring on mapped fault structures. We elaborate on building a self-consistent rate model for the hazardous crustal fault systems (e.g. Sumatra fault zone, Philippine fault zone) as well as the subduction zones, showcase some characteristics and sensitivities due to existing uncertainties in the rate and hazard space using a well selected suite of ground motion prediction equations. Finally, we analyze the source model by quantifying the contribution by source type (e.g., subduction zone, crustal fault) to typical risk metrics (e.g.,return period losses, average annual loss) and reviewing their relative impact on various lines of businesses.

  15. Estimation of seismic hazard in the Kaliningrad region

    Science.gov (United States)

    Ulomov, V. I.; Akatova, K. N.; Medvedeva, N. S.

    2008-09-01

    The paper discusses problems of seismic zoning of the Kaliningrad region, where a series of perceptible earthquakes occurred in 2004; the strongest event had a magnitude of M s = 4.3 and produced shakings of an intensity of 6 in the coastal zone of the Sambiiskii Peninsula, classified as a 5-intensity zone. The enhanced seismic effect is shown to be caused by bad ground conditions, long-term action of seismic effects, resonance phenomena, and other factors. To gain additional constraints on the seismic hazard degree in the Kaliningrad region, the paper discusses an improved version of the model of earthquake sources underlying the compilation of normative maps of seismic zoning (OSR-97). Modified fragments of OSR-97 probability maps of the Kaliningrad region are constructed at different levels of probability that the seismic effect indicated in the maps will be exceeded over 50 yr. It is shown that additional seismological investigations should be conducted in this region.

  16. Towards a Comprehensive Seismic Velocity Model for the Broader Africa-Eurasia Collision Region, to Improve Nuclear Explosion Monitoring

    Energy Technology Data Exchange (ETDEWEB)

    der Lee, S v; Flanagan, M P; Rodgers, A J; Pasyanos, M E; Marone, F; Romanowicz, B

    2005-07-13

    We report on progress towards a new, comprehensive three-dimensional model of seismic velocity in a broad region encompassing the Middle East, northern Africa, the Mediterranean Sea, the Levant, the Arabian Peninsula, the Turkish-Iranian Plateau, Indus Valley, and the Hindu Kush. Our model will be based on regional waveform fits, surface wave group velocity measurements, teleseismic arrival times of S and P waves, receiver functions, and published results from active source experiments. We are in the process of assembling each of these data sets and testing the joint inversion for subsets of the data. Seismograms come from a variety of permanent and temporary seismic stations in the region. Some of the data is easily accessible through, for example, IRIS, while collection of other data is more involved. This work builds on ongoing work by Schmid et al. (GJI, 2004, and manuscript in preparation). In these proceedings we highlight our data sets and their inferences, demonstrate the proposed new data-inversion modeling methodology, discuss results from preliminary inversions of subsets of the data, and demonstrate the prediction of arrival times with three-dimensional velocity models. We compare our preliminary inversion results to the results of Schmid et al., and the predicted arrival times to ground-truth data from the NNSA Knowledge Base. Our data sets are simultaneously redundant and highly complementary. The combined data coverage will ensure that our three-dimensional model comprises the crust, the upper mantle, including the transition zone, and the top of the lower mantle, with spatially varying, but useful resolution. The region of interest is one of the most structurally heterogeneous in the world. Continental collision, rifting and sea-floor spreading, back-arc spreading, oceanic subduction, rotating micro plates, continental shelf, and stable platforms, are just some of the region's characteristics. Seismicity and the distribution of seismic stations

  17. Crustal deformation in the south-central Andes backarc terranes as viewed from regional broad-band seismic waveform modelling

    Science.gov (United States)

    Alvarado, Patricia; Beck, Susan; Zandt, George; Araujo, Mario; Triep, Enrique

    2005-11-01

    The convergence between the Nazca and South America tectonic plates generates a seismically active backarc region near 31°S. Earthquake locations define the subhorizontal subducted oceanic Nazca plate at depths of 90-120 km. Another seismic region is located within the continental upper plate with events at depths Sierras Pampeanas and is responsible for the large earthquakes that have caused major human and economic losses in Argentina. South of 33°S, the intense shallow continental seismicity is more restricted to the main cordillera over a region where the subducted Nazca plate starts to incline more steeply, and there is an active volcanic arc. We operated a portable broad-band seismic network as part of the Chile-Argentina Geophysical Experiment (CHARGE) from 2000 December to 2002 May. We have studied crustal earthquakes that occurred in the back arc and under the main cordillera in the south-central Andes (29°S-36°S) recorded by the CHARGE network. We obtained the focal mechanisms and source depths for 27 (3.5 Sierras Pampeanas, over the flat-slab segment is dominated by reverse and thrust fault-plane solutions located at an average source depth of 20 km. One moderate-sized earthquake (event 02-117) is very likely related to the northern part of the Precordillera and the Sierras Pampeanas terrane boundary. Another event located near Mendoza at a greater depth (~26 km) (event 02-005) could also be associated with the same ancient suture. We found strike-slip focal mechanisms in the eastern Sierras Pampeanas and under the main cordillera with shallower focal depths of ~5-7 km. Overall, the western part of the entire region is more seismically active than the eastern part. We postulate that this is related to the presence of different pre-Andean geological terranes. We also find evidence for different average crustal models for those terranes. Better-fitting synthetic seismograms result using a higher P-wave velocity, a smaller average S-wave velocity and a

  18. Bayesian Inference of Seismic Sources Using a 3-D Earth Model for the Japanese Islands Region

    Science.gov (United States)

    Simutė, Saulė; Fichtner, Andreas

    2017-04-01

    Earthquake source inversion is an established problem in seismology. Nevertheless, one-dimensional Earth models are commonly used to compute synthetic data in point- as well as finite-fault inversions. Reliance on simplified Earth models limits the exploitable information to longer periods and as such, contributes to notorious non-uniqueness of finite-fault models. Failure to properly account for Earth structure means that inaccuracies in the Earth model can map into and pollute the earthquake source solutions. To tackle these problems we construct a full-waveform 3-D Earth model for the Japanese Islands region and infer earthquake source parameters in a probabilistic way using numerically computed 3-D Green's functions. Our model explains data from the earthquakes not used in the inversion significantly better than the initial model in the period range of 20-80 s. This indicates that the model is not over-fit and may thus be used for improved earthquake source inversion. To solve the forward problem, we pre-compute and store Green's functions with the spectral element solver SES3D for all potential source-receiver pairs. The exploitation of the Green's function database means that the forward problem of obtaining displacements is merely a linear combination of strain Green's tensor scaled by the moment tensor elements. We invert for ten model parameters - six moment tensors elements, three location parameters, and the time of the event. A feasible number of model parameters and the fast forward problem allow us to infer the unknowns using the Bayesian Markov chain Monte Carlo, which results in the marginal posterior distributions for every model parameter. The Monte Carlo algorithm is validated against analytical solutions for the linear test case. We perform the inversions using real data in the Japanese Islands region and assess the quality of the solutions by comparing the obtained results with those from the existing 1-D catalogues.

  19. Regional three-dimensional seismic velocity model of the crust and uppermost mantle of northern California

    Science.gov (United States)

    Thurber, C.; Zhang, H.; Brocher, T.; Langenheim, V.

    2009-01-01

    We present a three-dimensional (3D) tomographic model of the P wave velocity (Vp) structure of northern California. We employed a regional-scale double-difference tomography algorithm that incorporates a finite-difference travel time calculator and spatial smoothing constraints. Arrival times from earthquakes and travel times from controlled-source explosions, recorded at network and/or temporary stations, were inverted for Vp on a 3D grid with horizontal node spacing of 10 to 20 km and vertical node spacing of 3 to 8 km. Our model provides an unprecedented, comprehensive view of the regional-scale structure of northern California, putting many previously identified features into a broader regional context and improving the resolution of a number of them and revealing a number of new features, especially in the middle and lower crust, that have never before been reported. Examples of the former include the complex subducting Gorda slab, a steep, deeply penetrating fault beneath the Sacramento River Delta, crustal low-velocity zones beneath Geysers-Clear Lake and Long Valley, and the high-velocity ophiolite body underlying the Great Valley. Examples of the latter include mid-crustal low-velocity zones beneath Mount Shasta and north of Lake Tahoe. Copyright 2009 by the American Geophysical Union.

  20. Hypocenter relocation using a fast grid search method and a 3-D seismic velocity model for the Sumatra region

    Science.gov (United States)

    Nugroho, Hendro; Widiyantoro, Sri; Nugraha, Andri Dian

    2013-09-01

    Determination of earthquake hypocenter in Indonesia conducted by the Meteorological, Climatological, and Geophysical Agency (MCGA) has still used a 1-D seismic velocity model. In this research, we have applied a Fast Grid Search (FGM) method and a 3-D velocity model resulting from tomographic imaging to relocate earthquakes in the Sumatran region. The data were taken from the MCGA data catalog from 2009 to 2011 comprising of subduction zone and on land fault earthquakes with magnitude greater than 4 Mw. Our preliminary results show some significant changes in the depths of the relocated earthquakes which are in general deeper than the depths of hypocenters from the MCGA data catalog. The residual times resulting from the relocation process are smaller than those prior to the relocation. Encouraged by these results, we will continue to conduct hypocenter relocation for all events from the MCGA data catalog periodically in order to produce a new data catalog with good quality. We hope that the new data catalog will be useful for further studies.

  1. Hypocenter relocation using a fast grid search method and a 3-D seismic velocity model for the Sumatra region

    Energy Technology Data Exchange (ETDEWEB)

    Nugroho, Hendro [Study Program of Earth Sciences, Faculty of Earth Sciences and Technology, Institute of Technology Bandung, Jl. Ganesha No. 10, Bandung 40132, Indonesia and Meteorological, Climatological, and Geophysical Agency, Jl. Angkasa 1 No. 2, Kemayoran, Jakar (Indonesia); Widiyantoro, Sri [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jl. Ganesha No. 10, Bandung 40132 (Indonesia); Nugraha, Andri Dian [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technologyc Bandung, Jl. Ganesha No. 10, Bandung 40132 (Indonesia)

    2013-09-09

    Determination of earthquake hypocenter in Indonesia conducted by the Meteorological, Climatological, and Geophysical Agency (MCGA) has still used a 1-D seismic velocity model. In this research, we have applied a Fast Grid Search (FGM) method and a 3-D velocity model resulting from tomographic imaging to relocate earthquakes in the Sumatran region. The data were taken from the MCGA data catalog from 2009 to 2011 comprising of subduction zone and on land fault earthquakes with magnitude greater than 4 Mw. Our preliminary results show some significant changes in the depths of the relocated earthquakes which are in general deeper than the depths of hypocenters from the MCGA data catalog. The residual times resulting from the relocation process are smaller than those prior to the relocation. Encouraged by these results, we will continue to conduct hypocenter relocation for all events from the MCGA data catalog periodically in order to produce a new data catalog with good quality. We hope that the new data catalog will be useful for further studies.

  2. Regional Seismic Amplitude Modeling and Tomography for Earthquake-Explosion Discrimination

    Science.gov (United States)

    2008-09-01

    TJN, which are publicly available through data centers such as the Incorporated Research Institutions for Seismology (IRIS) and the Ocean Hemisphere...Regional body-wave attenuation using a coda source normalization method: application to MEDNET records of earthquakes in Italy , Geophys. Res

  3. Probabilistic seismic hazard maps for the North Balkan region

    Directory of Open Access Journals (Sweden)

    R. M. W. Musson

    1999-06-01

    Full Text Available A set of seismic hazard maps, expressed as horizontal peak ground acceleration, have been computed for a large area of Central and Eastern Europe covering the North Balkan area (Former Yugoslavia, Hungary, Romania. These are based on: a a compound earthquake catalogue for the region; b a seismic source model of 50 zones compiled on the basis of tectonic divisions and seismicity, and c a probabilistic methodology using stochastic (Monte Carlo modelling. It is found that the highest hazard in the region comes from intermediate focus earthquakes occurring in the Vrancea seismic zone; here the hazard exceeds 0.4 g at return periods of 475 years. Special account has been taken of the directional nature of attenuation from this source.

  4. High-Resolution Seismic Velocity and Attenuation Models of Eastern Tibet and Adjacent Regions (Post Print)

    Science.gov (United States)

    2012-06-04

    mantle in this region. Similarly, a high velocity and high Q block in southeastern Tibet around eastern Bangong-Nujiang Suture and Eastern Himalaya ...Similarly, a high velocity and high Q block in southeastern Tibet around eastern Bangong-Nujiang Suture and Eastern Himalaya Syntaxis correlates well...underthrusting Indian plate. Azimuthal fast directions are consistent at all depths up to approximately 200 km, which suggests a vertical coherent

  5. Methods for Estimating Mean Annual Rate of Earthquakes in Moderate and Low Seismicity Regions~

    Institute of Scientific and Technical Information of China (English)

    Peng Yanju; Zhang Lifang; Lv Yuejun; Xie Zhuojuan

    2012-01-01

    Two kinds of methods for determining seismic parameters are presented, that is, the potential seismic source zoning method and grid-spatially smoothing method. The Gaussian smoothing method and the modified Gaussian smoothing method are described in detail, and a comprehensive analysis of the advantages and disadvantages of these methods is made. Then, we take centrai China as the study region, and use the Gaussian smoothing method and potential seismic source zoning method to build seismic models to calculate the mean annual seismic rate. Seismic hazard is calculated using the probabilistic seismic hazard analysis method to construct the ground motion acceleration zoning maps. The differences between the maps and these models are discussed and the causes are investigated. The results show that the spatial smoothing method is suitable for estimating the seismic hazard over the moderate and low seismicity regions or the hazard caused by background seismicity; while the potential seismic source zoning method is suitable for estimating the seismic hazard in well-defined seismotectonics. Combining the spatial smoothing method and the potential seismic source zoning method with an integrated account of the seismicity and known seismotectonics is a feasible approach to estimate the seismic hazard in moderate and low seismicity regions.

  6. Interrelation between seismicity parameters and delimiting potential seismic sources in a seismic statistical region and its influence on seismic risk estimation

    Institute of Scientific and Technical Information of China (English)

    HUANG Wei-qiong; WU Xuan

    2005-01-01

    In the paper, we have discovered the abnormal area distribution features of maximum variation values of ground motion parameter uncertainty with different probabilities of exceedance in 50 years within the range of 100°~120°E,29°~42°N for the purpose to solve the problem that abnormal areas of maximum variation values of ground motion parameter uncertainties emerge in a certain cities and towns caused by seismicity parameter uncertainty in a seismic statistical region in an inhomogeneous distribution model that considers tempo-spatial nonuniformity of seismic activity. And we have also approached the interrelation between the risk estimation uncertainty of a site caused by seismicity parameter uncertainty in a seismic statistical region and the delimitation of potential sources, as well as the reasons for forming abnormal areas. The results from the research indicate that the seismicity parameter uncertainty has unequal influence on the uncertainty of risk estimation at each site in a statistical region in the inhomogeneous distribution model, which relates to the scheme for delimiting potential sources. Abnormal areas of maximum variation values of ground motion parameter uncertainty often emerge in the potential sources of Mu≥8 (Mu is upper limit of a potential source) and their vicinity. However, this kind of influence is equal in the homogeneous distribution model. The uncertainty of risk estimation of each site depends on its seat. Generally speaking, the sites located in the middle part of a statistical region are only related to the seismicity parameter uncertainty of the region, while the sites situated in or near the juncture of two or three statistical regions might be subject to the synthetic influences of seismicity parameter uncertainties of several statistical regions.

  7. Seismic modeling of carbonate outcrops

    Energy Technology Data Exchange (ETDEWEB)

    Stafleu, J.; Schlager, W.; Campbell, E.; Everts, A.J. (Vrije Universiteit, Amsterdam (Netherlands))

    1993-09-01

    Traditionally, seismic modeling has concentrated on one-dimensional borehole modeling and two-dimensional forward modeling of basic structural-stratigraphic schemes, which are directly compared with real seismic data. Two-dimensional seismic models based on outcrop observations may aid in bridging the gap between the detail of the outcrop and the low resolution of seismic lines. Examples include the Dolomites (north Italy), the High Atlas (Morocco), the Vercors (southeast France) and the Last chance Canyon (New Mexico). The seismic models generally are constructed using the following procedure: (1) construction of a detailed lithological model based on direct outcrop observations; (2) division of the lithological model into lithostratigraphic units, using master bedding planes and important facies transitions as boundaries; (3) assignment of petrophysical properties of these lithostratigraphic units; (4) computation of time sections of reflectivity, using different modeling techniques; and (5) convolution with source wavelets of different frequencies. The lithological detail modeled in the case studies lead to some striking results, particularly the discovery of pseudo-unconformities. Pseudo-unconformities are unconformities in seismics, but correspond to rapid changes of dip and facies in outcrop. None of the outcrop geometries studied were correctly portrayed seismically at 25 Hz frequency. However, in some instances the true relationship would emerge gradually at frequencies of 50 to 100 Hz. These results demonstrate that detailed, outcrop-derived/seismic models can reveal what stratigraphic relationships and features are likely to be resolved under ideal or less ideal conditions, and what pitfalls may befall the interpreter of real seismic data.

  8. Midget Seismic in Sandbox Models

    Science.gov (United States)

    Krawczyk, C. M.; Buddensiek, M. L.; Philipp, J.; Kukowski, N.; Oncken, O.

    2008-12-01

    Analog sandbox simulation has been applied to study geological processes to provide qualitative and quantitative insights into specific geological problems. In nature, the structures, which are simulated in those sandbox models, are often inferred from seismic data. With the study introduced here, we want to combine the analog sandbox simulation techniques with seismic physical modeling of those sandbox models. The long-term objectives of this approach are (1) imaging of seismic and seismological events of actively deforming and static 3D analogue models, and (2) assessment of the transferability of the model data to field data in order to improve field data acquisition and interpretation according to the addressed geological problem. To achieve this objective, a new midget-seismic facility for laboratory use was designed and developed, comprising a seismic tank, a PC control unit including piezo-electric transducers, and a positioning system. The first experiments are aimed at studying the wave field properties of the piezo- transducers in order to investigate their feasibility for seismic profiling. The properties investigated are their directionality and the change of waveform due to their size (5-12 mm) compared to the wavelengths (material properties and the effects of wave propagation in an-/isotropic media by physical studies, before we finally start using different seismic imaging and processing techniques on static and actively deforming 3D analog models.

  9. Modeling Regional Seismic Waves

    Science.gov (United States)

    1992-03-24

    are earth- quakes for a given long-period energy level and is attributed, in part, to the differences in characteristic tern ) oral and spatial source...McLaughlin, 1991) Mid various observational stndies ( Vih ,’elli, I1973, Stump, 1985; Taylor and lVandall, 1989; nI d P’alt oi, 199•!)) conclitde thati

  10. Modeling Regional Seismic Waves

    Science.gov (United States)

    1992-06-29

    80107 6 3.36 0.13 RAT minersiron 80305 11 4.40 0.05 YAT baseball 81015 10 4.18 0.07 YBT rousanne 81316 9 4.67 0.05 YBT jornada 82028 10 4.52 0.06 PBR...Livermore National Laborator ,- A Division of Maxwell Laboratory L-025 P.O. Box 1620 PO. Box 808 La Jolla, CA 92038-1620 Livermore, CA 945(50 Stephen Miller...for Earth Sciences S-CUBBED University of Southern California A Division of Maxwell Laborator .- University Park P.O. Box 1620 Los Angeles, CA 90089

  11. Cursory seismic drift assessment for buildings in moderate seismicity regions

    Institute of Scientific and Technical Information of China (English)

    Zhu Yong; R.K.L. Su; Zhou Fulin

    2007-01-01

    This paper outlines a methodology to assess the seismic drift of reinforced concrete buildings with limited structural and geotechnical information. Based on the latest and the most advanced research on predicting potential near-field and far field earthquakes affecting Hong Kong, the engineering response spectra for both rock and soil sites are derived. A new step-by-step procedure for displacement-based seismic hazard assessment of building structures is proposed to determine the maximum inter-storey drift demand for reinforced concrete buildings. The primary information required for this assessment is only the depth of the soft soil above bedrock and the height of the building. This procedure is further extended to assess the maximum chord rotation angle demand for the coupling beam of coupled shear wall or frame wall structures, which may be very critical when subjected to earthquake forces. An example is provided to illustrate calibration of the assessment procedure by using actual engineering structural models.

  12. Statistical evaluation of CTBT regional seismic monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, K.K.

    1996-09-01

    A global seismic monitoring system under a Comprehensive Test Ban Treaty (CTBT) is judged by its capability to detect, locate, and identify suspicious seismic events. Performance measures are those statistical objects that describe these capabilities. Performance criteria are the thresholds derived from the overall monitoring system goals, against which the evaluated performance measures are compared. This report proposes statistical objects for performance measurement of detection and location, a continuation of the research of Anderson and Anderson. A statistical methodology for calibrating regional station magnitudes to the worldwide teleseismic Mb scale is also proposed.

  13. Regional seismic wavefield computation on a 3-D heterogeneous Earth model by means of coupled traveling wave synthesis

    Science.gov (United States)

    Pollitz, F.F.

    2002-01-01

    I present a new algorithm for calculating seismic wave propagation through a three-dimensional heterogeneous medium using the framework of mode coupling theory originally developed to perform very low frequency (f seismic wavefield computation. It is a Greens function approach for multiple scattering within a defined volume and employs a truncated traveling wave basis set using the locked mode approximation. Interactions between incident and scattered wavefields are prescribed by mode coupling theory and account for the coupling among surface waves, body waves, and evanescent waves. The described algorithm is, in principle, applicable to global and regional wave propagation problems, but I focus on higher frequency (typically f ??????0.25 Hz) applications at regional and local distances where the locked mode approximation is best utilized and which involve wavefields strongly shaped by propagation through a highly heterogeneous crust. Synthetic examples are shown for P-SV-wave propagation through a semi-ellipsoidal basin and SH-wave propagation through a fault zone.

  14. Seismicity analysis in Indonesia region from high precision hypocenter location

    Science.gov (United States)

    Nugraha, Andri; Shiddiqi, Hasbi; Widiyantoro, Sri; Ramdhan, Mohamad; Wandono, Wandono

    2015-04-01

    As a complex tectonic region, Indonesia has a high seismicity rate which is related to subduction and collision as well as strike-slip fault. High-precision earthquake locations with adequate relocation method and proper velocity model are necessary for seismicity analysis. We used nearly 25,000 earthquakes that were relocated using double-difference method. In our relocation process, we employed teleseismic, regional, and local P-wave arrival times. Furthermore, we employed regional-global nested velocity models that take into account the subduction slab in the study region by using a 3D model for area inside and a 1D model for area outside Indonesia. Relocation results show shifted hypocenters that are generally perpendicular to the trench. Beneath western Sunda arc, the Wadati-Benioff Zone (WBZ) extents to a depth of about 300 km and depicts a gently dipping slab. The WBZ beneath eastern Sunda arc extends deeper to about 500 km and depicts a steep slab geometry. In the Sunda-Banda transition zone, we found anomalously low seismicity beneath the oceanic-continental transition region. The WBZ of the severely curved Banda arc extends to a depth of about 600 km and depicts a two-slab model. In the Molucca collision zone, seismicity clearly depicts two opposing slabs of the Molucca sea plate, i.e. to the east and to the west. Around Sulawesi region, most earthquakes are related to the north Sulawesi trench and depict subducted slab beneath the northern part of the island. In Sumatra region, we identified a seismic gap in the WBZ between 70 km and 150 km. Seismicity gaps are also detected beneath particular regions, e.g. Mentawai region, and several parts along the subducted slab. Similar to the Sumatra region, beneath eastern Sunda arc, seismic gap in WBZ is also detected but deeper, i.e. at depths of 150 km to 250 km. Furthermore, we used global centroid moment tensor catalog data available for earthquakes with magnitude 5.0 or greater. In general, focal mechanism

  15. Seismic source characterization for the 2014 update of the U.S. National Seismic Hazard Model

    Science.gov (United States)

    Moschetti, Morgan P.; Powers, Peter; Petersen, Mark D.; Boyd, Oliver; Chen, Rui; Field, Edward H.; Frankel, Arthur; Haller, Kathleen; Harmsen, Stephen; Mueller, Charles S.; Wheeler, Russell; Zeng, Yuehua

    2015-01-01

    We present the updated seismic source characterization (SSC) for the 2014 update of the National Seismic Hazard Model (NSHM) for the conterminous United States. Construction of the seismic source models employs the methodology that was developed for the 1996 NSHM but includes new and updated data, data types, source models, and source parameters that reflect the current state of knowledge of earthquake occurrence and state of practice for seismic hazard analyses. We review the SSC parameterization and describe the methods used to estimate earthquake rates, magnitudes, locations, and geometries for all seismic source models, with an emphasis on new source model components. We highlight the effects that two new model components—incorporation of slip rates from combined geodetic-geologic inversions and the incorporation of adaptively smoothed seismicity models—have on probabilistic ground motions, because these sources span multiple regions of the conterminous United States and provide important additional epistemic uncertainty for the 2014 NSHM.

  16. Seismic Physical Modeling Technology and Its Applications

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper introduces the seismic physical modeling technology in the CNPC Key Lab of Geophysical Exploration. It includes the seismic physical model positioning system, the data acquisition system, sources, transducers,model materials, model building techniques, precision measurements of model geometry, the basic principles of the seismic physical modeling and experimental methods, and two physical model examples.

  17. Damage Tensor Analysis on Regional Seismic Status

    Institute of Scientific and Technical Information of China (English)

    Zhong Jimao; Cheng Wanzheng

    2006-01-01

    In this paper, we researched the regional seismic status by using theories of the Damage Mechanics. The macroscopic damage status of the earth crust block, which is caused by earthquake fracture, is described with several concepts-the damage degree, the damage rate and the strain rate. In the earthquake process, the average strain rate of the studied block is equal to the sum of all seismic moment tensors of the earthquakes taking place in unit time and physical volume. To describe the anisotropy of microdamage of the crust block, we use the damage tensor that is expressed in the fissure density. By means of the transformation from the focal coordinate system to the observation system, we obtained the external normal vector of the focal fault plane expressed in its observation system and obtained the macrodamage degree of the researched block, which is calculated in dyadic. This provides a new analysis method for recognizing the underground damage status and the stress status.

  18. Probabilistic seismic hazard assessment of the Pyrenean region

    Science.gov (United States)

    Secanell, R.; Bertil, D.; Martin, C.; Goula, X.; Susagna, T.; Tapia, M.; Dominique, P.; Carbon, D.; Fleta, J.

    2008-07-01

    A unified probabilistic seismic hazard assessment (PSHA) for the Pyrenean region has been performed by an international team composed of experts from Spain and France during the Interreg IIIA ISARD project. It is motivated by incoherencies between the seismic hazard zonations of the design codes of France and Spain and by the need for input data to be used to define earthquake scenarios. A great effort was invested in the homogenisation of the input data. All existing seismic data are collected in a database and lead to a unified catalogue using a local magnitude scale. PSHA has been performed using logic trees combined with Monte Carlo simulations to account for both epistemic and aleatory uncertainties. As an alternative to hazard calculation based on seismic sources zone models, a zoneless method is also used to produce a hazard map less dependant on zone boundaries. Two seismogenic source models were defined to take into account the different interpretations existing among specialists. A new regional ground-motion prediction equation based on regional data has been proposed. It was used in combination with published ground-motion prediction equations derived using European and Mediterranean data. The application of this methodology leads to the definition of seismic hazard maps for 475- and 1,975-year return periods for spectral accelerations at periods of 0 (corresponding to peak ground acceleration), 0.1, 0.3, 0.6, 1 and 2 s. Median and percentiles 15% and 85% acceleration contour lines are represented. Finally, the seismic catalogue is used to produce a map of the maximum acceleration expected for comparison with the probabilistic hazard maps. The hazard maps are produced using a grid of 0.1°. The results obtained may be useful for civil protection and risk prevention purposes in France, Spain and Andorra.

  19. Seismic Imaging of Sandbox Models

    Science.gov (United States)

    Buddensiek, M. L.; Krawczyk, C. M.; Kukowski, N.; Oncken, O.

    2009-04-01

    Analog sandbox simulations have been applied to study structural geological processes to provide qualitative and quantitative insights into the evolution of mountain belts and basins. These sandbox simulations provide either two-dimensional and dynamic or pseudo-three-dimensional and static information. To extend the dynamic simulations to three dimensions, we combine the analog sandbox simulation techniques with seismic physical modeling of these sandbox models. The long-term objective of this approach is to image seismic and seismological events of static and actively deforming 3D analog models. To achieve this objective, a small-scale seismic apparatus, composed of a water tank, a PC control unit including piezo-electric transducers, and a positioning system, was built for laboratory use. For the models, we use granular material such as sand and glass beads, so that the simulations can evolve dynamically. The granular models are required to be completely water saturated so that the sources and receivers are directly and well coupled to the propagating medium. Ultrasonic source frequencies (˜500 kHz) corresponding to wavelengths ˜5 times the grain diameter are necessary to be able to resolve small scale structures. In three experiments of different two-layer models, we show that (1) interfaces of layers of granular materials can be resolved depending on the interface preparation more than on the material itself. Secondly, we show that the dilation between the sand grains caused by a string that has been pulled through the grains, simulating a shear zone, causes a reflection that can be detected in the seismic data. In the third model, we perform a seismic reflection survey across a model that contains both the prepared interface and a shear zone, and apply 2D-seismic reflection processing to improve the resolution. Especially for more complex models, the clarity and penetration depth need to be improved to study the evolution of geological structures in dynamic

  20. A Preliminary Study on Seismicity and Stages of Seismic Energy Accumulation in Seismotectonic Regions of Tianshan

    Institute of Scientific and Technical Information of China (English)

    Li Yingzhen; Shen Jun; Wang Haitao

    2006-01-01

    Using seismic parameters, the characteristics of the seismic activity in various seismotectonic regions of Tianshan were studied in this paper. These regions are going through different stages of seismic energy accumulation. Current seismic risk levels of these areas were analyzed synthetically by the tectonic movement rates, as well as the characteristics of the seismic activity and the recurrence intervals of strong earthquakes. We preliminarily studied the characteristics of seismic activity in different seismic energy accumulating stages. The result shows that the characteristics of the seismic activity in various seismotectonic regions of the Tianshan area are influenced, not only by the regional tectonic movement, but also by the energy accumulating stage of various seismic tectonics. In the intense tectonic movement areas, it is important to estimate its stage of energy accumulating in order to predict the upper limit of the potential earthquake magnitude. In the less intense tectonic movement areas, the estimating of the stage of energy accumulation will help us recognize the dangerous level of the potential strong earthquake. The study shows that the seismotectonic regions in southern Tianshan have reached the mid-stage and late-stage of energy accumulation, with a higher seismic activity and thus a higher seismic dangerous level than those in the northern and middle Tianshan. The earthquake risk of southern Tianshan is up to Ms7.0, while that of the middle Tianshan is up to Ms6.0 and that of northern Tianshan is only around Ms5.0 ~ 6.0.

  1. Validating induced seismicity forecast models - Induced Seismicity Test Bench

    CERN Document Server

    Kiraly-Proag, Eszter; Gischig, Valentin; Wiemer, Stefan; Karvounis, Dimitrios; Doetsch, Joseph

    2016-01-01

    Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. In this study, we propose an Induced Seismicity Test Bench to test and rank such models; this test bench can be used for model development, model selection, and ensemble model building. We apply the test bench to data from the Basel 2006 and Soultz-sous-For\\^ets 2004 geothermal stimulation projects, and we assess forecasts from two models: Shapiro and Smoothed Seismicity (SaSS) and Hydraulics and Seismics (HySei). These models incorporate a different mix of physics-based elements and stochastic representation of the induced sequences. Our results show that neither model is fully superior to the other. Generally, HySei forecasts the seismicity rate better after shut-in, but is only mediocre at forecasting the spatial distri...

  2. An improved 1-D seismic velocity model for seismological studies in the Campania-Lucania region (Southern Italy)

    Science.gov (United States)

    Matrullo, Emanuela; De Matteis, Raffaella; Satriano, Claudio; Amoroso, Ortensia; Zollo, Aldo

    2013-10-01

    We present a 1-D velocity model of the Earth's crust in Campania-Lucania region obtained by solving the coupled hypocentre-velocity inverse problem for 1312 local earthquakes recorded at a dense regional network. The model is constructed using the VELEST program, which calculates 1-D `minimum' velocity model from body wave traveltimes, together with station corrections, which account for deviations from the simple 1-D structure. The spatial distribution of station corrections correlates with the P-wave velocity variations of a preliminary 3-D crustal velocity model that has been obtained from the tomographic inversion of the same data set of P traveltimes. We found that station corrections reflect not only inhomogeneous near-surface structures, but also larger-scale geological features associated to the transition between carbonate platform outcrops at Southwest and Miocene sedimentary basins at Northeast. We observe a significant trade-off between epicentral locations and station corrections, related to the existence of a thick low-velocity layer to the NE. This effect is taken into account and minimized by re-computing station corrections, fixing the position of a subset of well-determined hypocentres, located in the 3-D tomographic model.

  3. Seismic Hazard Assessment in Stable Continental Regions of Northen Eurasia

    Science.gov (United States)

    Levshenko, V.; Yunga, S.

    2009-04-01

    Assessment of the seismic potential and related risk level of stable continental regions (SCR) is a highly complex problem, as the applicability of techniques developed for seismically active areas to the areas that have no or limited seismic records is still under discussion. The seismotectonic data of the SCR are very poor because of low seismic activity and an insufficient seismological monitoring system. On the other hand, the geological knowledge is rather good owing to extensive geological and geophysical surveys held during the past decades. Digital data base is compiled from all collected data. Procedure of its interpretation use current internationally recognized methods and criteria and include several stages. 1) Microearthquake detection on the base of seismograms which used polarization analysis, artificial intellect method, wavelet analysis. 2) Paleoearthquakes, prehistorical, historical and instrumentally recorded earthquakes are investigated. 3) The faults capability are analyzed and appropriate seismotectonic model is created. 4) Amplitudes of neotectonic vertical movements, basement and Moho boundaries are interpreted numerically in terms of deformation of earth crust in the investigated region through curvatures calculations. 5) Seismotectonic deformation rate (seismic strain release) are estimated analytically and thus it dependence from maximum earthquake magnitude (Mmax) and the seismic activity parameters are derived. 6) Maximum earthquake potential Mmax of capable faults is evaluated on the base of comparison of geological and seismic deformation. Magnitude of design basis earthquake is estimated using recurrence plot. 7) Engineering Seismology Studies included estimation of peak ground acceleration (PGA) and duration of strong shaking. The PGA is derived from the regional attenuation lows for ground motion versus distance. We apply the above approach to the several critical facilities which have been investigated during last years. The

  4. Reassessment of probabilistic seismic hazard in the Marmara region

    Science.gov (United States)

    Kalkan, E.; Gulkan, Polat; Yilmaz, N.; Celebi, M.

    2009-01-01

    In 1999, the eastern coastline of the Marmara region (Turkey) witnessed increased seismic activity on the North Anatolian fault (NAF) system with two damaging earthquakes (M 7.4 Kocaeli and M 7.2 D??zce) that occurred almost three months apart. These events have reduced stress on the western segment of the NAF where it continues under the Marmara Sea. The undersea fault segments have been recently explored using bathymetric and reflection surveys. These recent findings helped scientists to understand the seismotectonic environment of the Marmara basin, which has remained a perplexing tectonic domain. On the basis of collected new data, seismic hazard of the Marmara region is reassessed using a probabilistic approach. Two different earthquake source models: (1) the smoothed-gridded seismicity model and (2) fault model and alternate magnitude-frequency relations, Gutenberg-Richter and characteristic, were used with local and imported ground-motion-prediction equations. Regional exposure is computed and quantified on a set of hazard maps that provide peak horizontal ground acceleration (PGA) and spectral acceleration at 0.2 and 1.0 sec on uniform firm-rock site condition (760 m=sec average shear wave velocity in the upper 30 m). These acceleration levels were computed for ground motions having 2% and 10% probabilities of exceedance in 50 yr, corresponding to return periods of about 2475 and 475 yr, respectively. The maximum PGA computed (at rock site) is 1.5g along the fault segments of the NAF zone extending into the Marmara Sea. The new maps generally show 10% to 15% increase for PGA, 0.2 and 1.0 sec spectral acceleration values across much of Marmara compared to previous regional hazard maps. Hazard curves and smooth design spectra for three site conditions: rock, soil, and soft-soil are provided for the Istanbul metropolitan area as possible tools in future risk estimates.

  5. Seismic transducer modeling using ABAQUS

    Energy Technology Data Exchange (ETDEWEB)

    Stephen R. Novascone

    2004-05-01

    A seismic transducer, known as an orbital vibrator, consists of a rotating imbalance driven by an electric motor. When suspended in a liquid-filled wellbore, vibrations of the device are coupled to the surrounding geologic media. In this mode, an orbital vibrator can be used as an efficient rotating dipole source for seismic imaging. Alternately, the motion of an orbital vibrator is affected by the physical properties of the surrounding media. From this point of view, an orbital vibrator can be used as a stand-alone sensor. The reaction to the surroundings can be sensed and recorded by geophones inside the orbital vibrator. These reactions are a function of the media’s physical properties such as modulus, damping, and density, thereby identifying the rock type. This presentation shows how the orbital vibrator and surroundings were modeled with an ABAQUS acoustic FEM. The FEM is found to compare favorably with theoretical predictions. A 2D FEM and analytical model are compared to an experimental data set. Each model compares favorably with the data set.

  6. Early seismicity of the Scottish Borders Region

    Directory of Open Access Journals (Sweden)

    R. M. W. Musson

    2004-06-01

    Full Text Available This paper considers the seismicity of Southern Scotland and Northern England up to the year 1750. This area was formerly a border area between two states that eventually became politically united. Much of the area is uplands, and the seismicity is moderate to low. This makes for some problems in studying historical seismicity, yet the area provides a number of case studies of general interest in the field of historical seismology, including a rare case of being able to track down a «missing» earthquake.

  7. Indication to distinguish the burst region of coal gas from seismic data

    Institute of Scientific and Technical Information of China (English)

    CHENG Jian-yuan; TANG Hong-wei; XU Lin; LI Yan-fang

    2009-01-01

    The velocity of an over-burst coal seam is about 1/3 compared to a normal coal seam based on laboratory test results. This can be considered as a basis to confirm the area of coal and gas burst by seismic exploration technique. Similarly, the simulation result of the theoretical seismic model shows that there is obvious distinction between over-burst coal and normal coal based on the coal reflection's travel-time, energy and frequency. The results from the actual seismic data acquired in the coal and gas over-burst cases is con-sistent with that of the laboratory and seismic modeling; that is, in the coal and gas burst region, seismic reflection travel time is delayed, seismic amplitude is weakened and seis-mic frequency is reduced. Therefore, it can be concluded that seismic exploration tech-nique is promising for use in distinguishing coal and gas over-burst regions based on the variation of seismic reflection travel time, amplitude and frequency.

  8. Indication to distinguish the burst region of coal gas from seismic data

    Energy Technology Data Exchange (ETDEWEB)

    Jian-yuan Cheng; Hong-wei Tang; Lin Xu; Yan-fang Li [China Coal Research Institute, Xi' an (China). Xi' an Research Institute

    2009-09-15

    The velocity of an over-burst coal seam is about 1/3 compared to a normal coal seam based on laboratory test results. This can be considered as a basis to confirm the area of coal and gas burst by seismic exploration technique. Similarly, the simulation result of the theoretical seismic model shows that there is obvious distinction between over-burst coal and normal coal based on the coal reflection's travel-time, energy and frequency. The results from the actual seismic data acquired in the coal and gas over-burst cases is consistent with that of the laboratory and seismic modeling; that is, in the coal and gas burst region, seismic reflection travel time is delayed, seismic amplitude is weakened and seismic frequency is reduced. Therefore, it can be concluded that seismic exploration technique is promising for use in distinguishing coal and gas over-burst regions based on the variation of seismic reflection travel time, amplitude and frequency. 7 refs., 6 figs.

  9. Seismic Radiation from Crack Coalescence Model and Reconstruction of Seismically Equivalent Single Crack Model

    Science.gov (United States)

    Kame, N.; Uchida, K.

    2006-12-01

    We simulate dynamic rupture propagation in which two mode II cracks coalesce on a planar fault using a boundary integral equation method. Our main interests are in the rupture complexity and resultant seismic radiation due to coalescence and in the reconstruction of seismically equivalent another dynamic model that could be inferred only from the waveforms. First we analyze crack coalescence model (CCM) with homogeneous source parameters except on two pre- slipped regions. In CCM, a main crack nucleates, propagates and coalesces with a nucleating subsidiary crack. Our analysis shows that local high slip-rate pulse is generated by coalescence and a secondary Rayleigh slip pulse subsequently begins to propagate trailing the rupture front. Second we reconstruct a single crack model (SCM) with heterogeneous source parameters that can reproduce the same slip-rate history in CCM, that is, both models are seismically equivalent. In SCM we found singular increase in the stress drop and sudden decrease in the strength excess corresponding to the coalescence pulse region, which means that these two inhomogeneities appeared in SCM originally resulted from the stress interaction between approaching crack tips in CCM. Third we synthesize seismic radiation from CCM and successfully identify distinct phases associated with two pulses: the coalescence pulse phase shows seismic radiation similar to the stopping phase that has a typical ω-2 behavior at high frequency, which is also consistent with theoretically predicted radiation by the singular stress drop in SCM. Rayleigh slip-pulse phase appears dominantly in transverse component with strong forward directivity similar to rupture front phase although disappears in parallel component except very near the fault.

  10. Global test of seismic static stress triggering model

    Institute of Scientific and Technical Information of China (English)

    万永革; 吴忠良; 周公威; 黄静; 秦立新

    2002-01-01

    Seismic static stress triggering model is tested using Harvard centroid moment tensor (CMT) solution catalogue of 1976~2000 and concept of (earthquake doublet(. Result shows that seismic static stress triggering effect does exist in the view of global earthquakes, but the effect is very weak. Dividing the earthquakes into thrust focal mechanism, normal focal mechanism, strike-slip focal mechanism, we find that non-strike-slip focal mechanism earthquakes have significant triggering effect, whereas, the triggering effect in strike-slip focal mechanism earthquakes is not obvious. Divided the subsequent events delay time of (earthquake doublet( into 5 classes of t(1, t<1, t(10, t<10, 1(t(10 (t is in unit of d), then seismic static stress triggering effect does not change with delay time in short time period after earthquakes. The research on seismic static stress triggering in different regions of the world indicates that triggering effect is significant in subduction belts. Seismic static stress triggering model is tested by using (earthquake doublets( in China and its adjacent region. The result indicates that seismic static stress triggering effect cannot be observed easily in China and its adjacent region due to the seismic focal mechanism type (most of the earthquakes are strike-slip earthquakes).

  11. Seismic waveform modeling over cloud

    Science.gov (United States)

    Luo, Cong; Friederich, Wolfgang

    2016-04-01

    With the fast growing computational technologies, numerical simulation of seismic wave propagation achieved huge successes. Obtaining the synthetic waveforms through numerical simulation receives an increasing amount of attention from seismologists. However, computational seismology is a data-intensive research field, and the numerical packages usually come with a steep learning curve. Users are expected to master considerable amount of computer knowledge and data processing skills. Training users to use the numerical packages, correctly access and utilize the computational resources is a troubled task. In addition to that, accessing to HPC is also a common difficulty for many users. To solve these problems, a cloud based solution dedicated on shallow seismic waveform modeling has been developed with the state-of-the-art web technologies. It is a web platform integrating both software and hardware with multilayer architecture: a well designed SQL database serves as the data layer, HPC and dedicated pipeline for it is the business layer. Through this platform, users will no longer need to compile and manipulate various packages on the local machine within local network to perform a simulation. By providing users professional access to the computational code through its interfaces and delivering our computational resources to the users over cloud, users can customize the simulation at expert-level, submit and run the job through it.

  12. 3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

    Science.gov (United States)

    Frantzeskakis, Theofanis; Konstantaras, Anthony

    2015-04-01

    During the last few years rapid steps have been taken towards drilling for oil in the western Mediterranean sea. Since most of the countries in the region benefit mainly from tourism and considering that the Mediterranean is a closed sea only replenishing its water once every ninety years careful measures are being taken to ensure safe drilling. In that concept this research work attempts to derive a three dimensional model of the seismically active parts of the underlying underground faults in areas of petroleum interest. For that purpose seismic spatio-temporal clustering has been applied to seismic data to identify potential distinct seismic regions in the area of interest. Results have been coalesced with two dimensional maps of underground faults from past surveys and seismic epicentres, having followed careful reallocation processing, have been used to provide information regarding the vertical extent of multiple underground faults in the region of interest. The end product is a three dimensional map of the possible underground location and extent of the seismically active parts of underground faults. Indexing terms: underground faults modelling, seismic data mining, 3D visualisation, active seismic source mapping, seismic hazard evaluation, dangerous phenomena modelling Acknowledgment This research work is supported by the ESPA Operational Programme, Education and Life Long Learning, Students Practical Placement Initiative. References [1] Alves, T.M., Kokinou, E. and Zodiatis, G.: 'A three-step model to assess shoreline and offshore susceptibility to oil spills: The South Aegean (Crete) as an analogue for confined marine basins', Marine Pollution Bulletin, In Press, 2014 [2] Ciappa, A., Costabile, S.: 'Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)', Marine Pollution Bulletin, vol. 84 (1-2), pp. 44-55, 2014 [3] Ganas, A., Karastathis, V., Moshou, A., Valkaniotis, S., Mouzakiotis

  13. Seismic Tomography of Siyazan - Shabran Oil and Gas Region Of Azerbaijan by Data of The Seismic Stations

    Science.gov (United States)

    Yetirmishli, Gurban; Guliyev, Ibrahim; Mammadov, Nazim; Kazimova, Sabina; Ismailova, Saida

    2016-04-01

    The main purpose of the research was to build a reliable 3D model of the structure of seismic velocities in the earth crust on the territory of Siyazan-Shabran region of Azerbaijan, using the data of seismic telemetry stations spanning Siyazan-Shabran region (Siyazan, Altiagaj, Pirgulu, Guba, Khinalig, Gusar), including 7 mobile telemetry seismic stations. Interest to the problem of research seismic tomography caused by applied environmental objectives, such as the assessment of geological risks, engineering evaluation (stability and safety of wells), the task of exploration and mining operations. In the study region are being actively developed oil fields, and therefore, there is a risk of technogenic earthquakes. It was performed the calculation of first arrival travel times of P and S waves and the corresponding ray paths. Calculate 1D velocity model which is the initial model as a set of horizontal layers (velocity may be constant or changed linearly with depth on each layer, gaps are possible only at the boundaries between the layers). Have been constructed and analyzed the horizontal sections of the three-dimensional velocity model at different depths of the investigated region. By the empirical method was proposed density model of the sedimentary rocks at depths of 0-8 km.

  14. Seismic Imaging and Seismicity Analysis in Beijing-Tianjin-Tangshan Region

    Directory of Open Access Journals (Sweden)

    Xiangwei Yu

    2011-01-01

    Full Text Available In this study a new tomographic method is applied to over 43,400 high-quality absolute direct P arrival times and 200,660 relative P arrival times to determine detailed 3D crustal velocity structures as well as the absolute and relative hypocenter parameters of 2809 seismic events under the Beijing-Tianjin-Tangshan region. The inferred velocity model of the upper crust correlates well with the surface geological and topographic features in the BTT region. In the North China Basin, the depression and uplift areas are imaged as slow and fast velocities, respectively. After relocation, the double-difference tomography method provides a sharp picture of the seismicity in the BTT region, which is concentrated along with the major faults. A broad low-velocity anomaly exists in Tangshan and surrounding area from 20 km down to 30 km depth. Our results suggest that the top boundary of low-velocity anomalies is at about 25.4 km depth. The event relocations inverted from double-difference tomography are clusted tightly along the Tangshan-Dacheng Fault and form three clusters on the vertical slice. The maximum focal depth after relocation is about 25 km depth in the Tangshan area.

  15. Toward Building a New Seismic Hazard Model for Mainland China

    Science.gov (United States)

    Rong, Y.; Xu, X.; Chen, G.; Cheng, J.; Magistrale, H.; Shen, Z.

    2015-12-01

    At present, the only publicly available seismic hazard model for mainland China was generated by Global Seismic Hazard Assessment Program in 1999. We are building a new seismic hazard model by integrating historical earthquake catalogs, geological faults, geodetic GPS data, and geology maps. To build the model, we construct an Mw-based homogeneous historical earthquake catalog spanning from 780 B.C. to present, create fault models from active fault data using the methodology recommended by Global Earthquake Model (GEM), and derive a strain rate map based on the most complete GPS measurements and a new strain derivation algorithm. We divide China and the surrounding regions into about 20 large seismic source zones based on seismotectonics. For each zone, we use the tapered Gutenberg-Richter (TGR) relationship to model the seismicity rates. We estimate the TGR a- and b-values from the historical earthquake data, and constrain corner magnitude using the seismic moment rate derived from the strain rate. From the TGR distributions, 10,000 to 100,000 years of synthetic earthquakes are simulated. Then, we distribute small and medium earthquakes according to locations and magnitudes of historical earthquakes. Some large earthquakes are distributed on active faults based on characteristics of the faults, including slip rate, fault length and width, and paleoseismic data, and the rest to the background based on the distributions of historical earthquakes and strain rate. We evaluate available ground motion prediction equations (GMPE) by comparison to observed ground motions. To apply appropriate GMPEs, we divide the region into active and stable tectonics. The seismic hazard will be calculated using the OpenQuake software developed by GEM. To account for site amplifications, we construct a site condition map based on geology maps. The resulting new seismic hazard map can be used for seismic risk analysis and management, and business and land-use planning.

  16. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    Energy Technology Data Exchange (ETDEWEB)

    Lestari, Titik, E-mail: t2klestari@gmail.com [Meteorological Climatological and Geophysical Agency (MCGA), Jalan Angkasa I No.2 Kemayoran, Jakarta Pusat, 10720 (Indonesia); Faculty of Earth Science and Technology, Bandung Institute of Technology, Jalan Ganesa No.10, Bandung 40132 (Indonesia); Nugraha, Andri Dian, E-mail: nugraha@gf.itb.ac.id [Global Geophysical Research Group, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Jalan Ganesa 10 Bandung 40132 (Indonesia)

    2015-04-24

    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA’s) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 – April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  17. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    Science.gov (United States)

    Lestari, Titik; Nugraha, Andri Dian

    2015-04-01

    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA's) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 - April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  18. Limits of the seismogenic zone in the epicentral region of the 26 December 2004 great Sumatra-Andaman earthquake: Results from seismic refraction and wide-angle reflection surveys and thermal modeling

    CERN Document Server

    Klingelhoefer, Frauke; Ladage, S; Dessa, J -X; Graindorge, David; Franke, D; André, C; Permana, Haryadi; Yudistira, T; Chauhan, Ajay; 10.1029/2009JB006569

    2010-01-01

    The 26 December 2004 Sumatra earthquake (Mw = 9.1) initiated around 30 km depth and ruptured 1300 km of the Indo-Australian Sunda plate boundary. During the Sumatra OBS (ocean bottom seismometer) survey, a wide angle seismic profile was acquired across the epicentral region. A seismic velocity model was obtained from combined travel time tomography and forward modeling. Together with reflection seismic data from the SeaCause II cruise, the deep structure of the source region of the great earthquake is revealed. Four to five kilometers of sediments overlie the oceanic crust at the trench, and the subducting slab can be imaged down to a depth of 35 km. We find a crystalline backstop 120 km from the trench axis, below the fore arc basin. A high velocity zone at the lower landward limit of the raycovered domain, at 22 km depth, marks a shallow continental Moho, 170 km from the trench. The deep structure obtained from the seismic data was used to construct a thermal model of the fore arc in order to predict the li...

  19. Regional tectonics of the Coso geothermal area along the intracontinental plate boundary in central eastern California: Three-dimensional V_p and V_p/V_s models, spatial-temporal seismicity patterns, and seismogenic deformation

    OpenAIRE

    Hauksson, Egill; Unruh, Jeffrey

    2007-01-01

    We synthesize the tectonics of the southern Walker Lane belt and Coso Range in central eastern California using regional earthquake data. First, we invert for three-dimensional models of the V_p and V_p/V_s structure of the upper and middle crust. Using these models, we also determine three-dimensional Vs and Poisson’s ratio models. The changes in seismic velocities across the region are small, except for low velocities in sedimentary basins and a ∼2-km positive elevation of the basement velo...

  20. Virginia Regional Seismic Network. Final report (1986--1992)

    Energy Technology Data Exchange (ETDEWEB)

    Bollinger, G.A.; Sibol, M.S.; Chapman, M.C.; Snoke, J.A. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (US). Seismological Observatory

    1993-07-01

    In 1986, the Virginia Regional Seismic Network was one of the few fully calibrated digital seismic networks in the United States. Continued operation has resulted in the archival of signals from 2,000+ local, regional and teleseismic sources. Seismotectonic studies of the central Virginia seismic zone showed the activity in the western part to be related to a large antiformal structure while seismicity in the eastern portion is associated spatially with dike swarms. The eastern Tennessee seismic zone extends over a 300x50 km area and is the result of a compressive stress field acting at the intersection between two large crustal blocks. Hydroseismicity, which proposes a significant role for meteoric water in intraplate seismogenesis, found support in the observation of common cyclicities between streamflow and earthquake strain data. Seismic hazard studies have provided the following results: (1) Damage areas in the eastern United States are three to five times larger than those observed in the west. (2) Judged solely on the basis of cataloged earthquake recurrence rates, the next major shock in the southeast region will probably occur outside the Charleston, South Carolina area. (3) Investigations yielded necessary hazard parameters (for example, maximum magnitudes) for several sites in the southeast. Basic to these investigations was the development and maintenance of several seismological data bases.

  1. Regional estimation of Q from seismic coda observations by the Gauribidanur seismic array (southern India)

    Science.gov (United States)

    Tripathi, Jayant Nath; Ugalde, Arantza

    2004-07-01

    Attenuation properties of the lithosphere in southern India are estimated from 1219 vertical-component, short-period observations of microearthquake codas recorded by the Gauribidanur seismic array. The magnitudes of the earthquakes range from 0.3 to 3.7 and have focal depths less than 10 km. Coda-wave attenuation ( Qc-1) is estimated by means of a single isotropic scattering method and a multiple lapse time window analysis based on the hypothesis of multiple isotropic scattering and uniform distribution of scatterers is used to estimate the contribution of intrinsic absorption ( Qi-1) and scattering ( Qs-1) to total attenuation ( Qt-1). All the attenuation parameters are estimated, as a function of frequency for hypocentral distances up to 255 km. Results show a frequency dependent relation of the Qc-1 values in the range 1-10 Hz that fit the power law Q -1(f)=Q 0-1(f/f 0) ηA Q 0-1 value of 0.014 and a decrease of f-1.2 have been found using data from the whole region. On the other hand, scattering attenuation is found to be greater than intrinsic absorption for all the frequency bands. A high value of the seismic albedo (which ranges from 0.68 to 1) is found which indicates that scattering is the dominant effect in the study region. Nevertheless, the attenuation parameters estimated are much lower than the obtained for other regions in the world. On the other hand, the observed energy at 0-15 s from the S-wave arrival time bends significantly downward with decreasing distance. In order to clarify this phenomenon, there is a need to take into account the vertical varying velocity structure in the theoretical model.

  2. Detection of atypical seismic events on a regional scale

    Science.gov (United States)

    Solano-Hernandez, E. A.; Hjorleifsdottir, V.; Perez-Campos, X.; Iglesias, A.

    2013-12-01

    We propose an event-detection algorithm to locate seismic events on a regional scale. Our goal is to identify non-impulsive or 'atypical' events which are not detected by regional or global networks, due to their low P-wave amplitude. Ekstrom (2006) has developed and implemented a method to detect and locate sources of long-period seismic surface waves on a global scale. Atypical events are generated by, for example, rapid glacial movements (Ekstrom, et al., 2003; Ekstrom, et al., 2006), volcanic events (Schuler and Ekstrom, 2009) and landslides (Ekstrom and Stark, 2013). Furthermore, non-impulsive earthquakes have been located on oceanic transform faults (Abercrombie and Ekstrom, 2001). The current method (Ekstrom, 2006), that is applied on the scale of the globe, routinely detects events with magnitudes around Mw 5 and larger. In this work we wish to lower the detection threshold by using shorter period records registered by regional networks. The difficulty lies in that the shorter period records are strongly influenced by the heterogeneous crust and upper mantle, which need to be accounted for in the modeling process. Our proposed method involves first computing full waveforms, Green's functions or moment tensor responses, between a grid of test locations and existing seismic stations in a 3D medium. We then effectively back propagate observed data through cross correlation with the responses, obtaining a function that localizes in time and space at the source. Our method is a variant of the timereversal method presented by, for example, McMechan (1982), Tromp et al. (2005), Larmat et al. (2006), Gajewski and Tessmer (2005) and Kim et al. (2010). To calibrate the various parameters used by the detection method, we use the aftershocks sequence of the March 20, 2012 Ometepec, Guerrero, Mexico earthquake, recorded by the SSN (Mexican National Network). The lively aftershock sequence provided us with many events of different magnitudes, all occurring approximately

  3. Development of seismic analysis model of LMFBR and seismic time history response analysis

    Energy Technology Data Exchange (ETDEWEB)

    Koo, K. H.; Lee, J. H.; Yoo, B. [KAERI, Taejon (Korea, Republic of)

    2001-05-01

    The main objective of this paper is to develop the seismic analysis model of KALIMER reactor structures including the primary coolant of sodium and to evaulate the seismic responses of the maximum peak acceleration and the relative displacements by the time history seismic response analysis. The seismic time history response analyses were carried out for both cases of the seismic isolation design and the non-isolation one to verify the seismic isolation performance. From the results of seismic response analysis using the developed seismic analysis model, it is clearly verified that the seismic isolation design gives very significantly reduced seismic responses compared with the non-isolation design. All design criteria for the relative displacement repsonse were satisfied for KALIMER reactor structures.

  4. Seismicity surveying in central and north mexico region

    Science.gov (United States)

    Gómez, J. M.; Guzmán, M.; Nieto, A.; Zúñiga, R.; Alaniz, S.; Barboza, R.

    2003-04-01

    The seismic nature of Central Mexico is poorly understood due to insufficient sampling. This region is characterized by a very low deformation rate. The seismic activity is variable and ranges from microseismicity to large earthquakes. Some large earthquakes have occurred with an unknown returning period; structural studies show this recurrence could range from hundreds to thousands of years. Some authors argue that there is not connection between ancient and recent activity. We carried out several seismic surveys in part of the TransMexican Volcanic Belt (TMVB) and the Altiplano Central. We installed a temporal network, in order to record spatial seismic distribution. This network consists of 3-5 short period instruments, consisting of triaxial digital velocity recorders (0.01-4.5 Hz). We registered several swarms; one took place in Guanajuato and lasted for 2 weeks. Another crisis occurred at the northern limit of the TMVB at Sierra Gorda. Over five weeks several micro-earthquakes M < 2 were felt with anomaously high intensity. Relocated seismicity shows very shallow (< 10km) activity. The regional crust conditions appear to be roughly uniform even though the seismicity varies significantly. In some cases like seismic swarms, several microearthquakes are aligned, and seem to be quasi-parallel to the direction of the fault strike, some other times they are perpendicular. However, surface ruptures associated to earthquakes are not observed to confirm this. Then, a challenge is to locate the seismogenic structures, basically because of the surface structures are too old to be still active. Increased seismotectonic knowledge of this region may give further insight into the details of the interaction between surface structures driven by the regional stress field.

  5. A probabilistic seismic hazard map of India and adjoining regions

    Directory of Open Access Journals (Sweden)

    H. K. Gupta

    1999-06-01

    Full Text Available This paper presents the results of an exercise carried out under GSHAP, over India and adjoining regions bound by 0°N-40°N and 65°E-100°E. A working catalogue of main shocks was prepared by merging the local catalogues with the NOAA catalogue, and removing duplicates, aftershocks and earthquakes without any magnitude. Eighty six potential seismic source zones were delineated based on the major tectonic features and seismicity trends. Using the probabilistic hazard assessment approach of McGuire, adopted by GSHAP, the Peak Ground Accelerations (PGA were computed for 10% probability of exceedance in 50 years, at locations defined by a grid of 0.5° x 0.5°. Since no reliable estimates of attenuation values are available for the Indian region, the attenuation relation of Joyner and Boore (1981 was used. The PGA values over the grid points were contoured to obtain a seismic hazard map. The hazard map depicts that a majority of the Northern Indian plate boundary region and the Tibetan plateau region have hazard level of the order of 0.25 g with prominent highs of the order of 0.35-0.4 g in the seismically more active zones like the Burmese arc, Northeastern India and Hindukush region. In the Indian shield, the regional seismic hazard, covering a major area, is of the order of 0.05-0.1 g whereas some areas like Koyna depict hazard to the level of 0.2 g. The present map can be converted into a conventional seismic zoning map having four zones with zone factors of 0.1 g, 0.2 g, 0.3 g and 0.4 g respectively.

  6. Seismicity Surveying in Central and North Mexico Regions

    Science.gov (United States)

    Nieto-Samaniego, A.; Gomez-Gonzalez, J. M.; Guzman-Speziale, M.; Zuniga, R.; Alaniz-Alvarez, S.; Barboza, R.; Davalos, O.

    2003-12-01

    The seismic nature of Central Mexico is poorly understood due to insufficient sampling. We carried out a seismic survey in part of the TransMexican Volcanic Belt (TMVB) and the Central Altiplano. These regions are characterized by a very low deformation rates. Seismic activity is variable and ranges from microseismicity to large earthquakes, but no large historic earthquake has been instrumentally recorded. Only few direct observations such as intensity reconstructions and recent paleoseismic studies (e.g. the Acambay-Tixmadej earthquake of 1912) are available. Large earthquakes have occurred but their recurrence period is unknown; structural studies show this recurrence could range from hundreds to thousands of years. In order to understand the regional seismic behavior, we installed a temporal network. This network consists of 3-5 short period instruments, consisting of 16-bits triaxial digital velocity recorders (0.01-4.5 Hz). We registered several seismic sequences over a period of several months. One of them took place in Guanajuato within a graben structure in the TMVB and lasted for 2 weeks. Another sequence occurred at the northern limit of the TMVB in the Sierra Gorda. Over five weeks, several micro-earthquakes M Sierra Gorda, the event distribution is aligned along a small valley, but perpendicular to the main structural grain imposed by the Sierra Madre Oriental range. In no instances have surface ruptures been observed; those seismogenic structures could be blind ones. A challenge is to locate this structures which are may be too old to be still active. Increased seismotectonic knowledge of this region will yield further insight into the details of the interaction between surface structures driven by the regional stress field. Our results provide evidence that the region requires more intensive seismic surveying, and in some cases that some structures have been reactivated recently.

  7. Lithospheric structure models applied for locating the Romanian seismic events

    Directory of Open Access Journals (Sweden)

    V. Oancea

    1994-06-01

    Full Text Available The paper presents our attempts made for improving the locations obtained for local seismic events, using refined lithospheric structure models. The location program (based on Geiger method supposes a known model. The program is run for some seismic sequences which occurred in different regions, on the Romanian territory, using for each of the sequences three velocity models: 1 7 layers of constant velocity of seismic waves, as an average structure of the lithosphere for the whole territory; 2 site dependent structure (below each station, based on geophysical and geological information on the crust; 3 curves deseribing the dependence of propagation velocities with depth in the lithosphere, characterizing the 7 structural units delineated on the Romanian territory. The results obtained using the different velocity models are compared. Station corrections are computed for each data set. Finally, the locations determined for some quarry blasts are compared with the real ones.

  8. Extending Regional Seismic Travel Time (RSTT) Tomography to New Regions

    Science.gov (United States)

    2011-09-01

    Seism . Soc. Am. 59, 1365–1398. Flanagan, M. P., D. A. Dodge, and S. C. Myers (2008). GT merge process: Version 2.0, LLNL technical report, LLNL-TR...Validation of regional and teleseismic travel-time models by relocating ground-truth events, Bull. Seism . Soc. Amer. 94: 897–919. Zhao, L.-S. (1993

  9. Seismic Hazard analysis of Adjaria Region in Georgia

    Science.gov (United States)

    Jorjiashvili, Nato; Elashvili, Mikheil

    2014-05-01

    The most commonly used approach to determining seismic-design loads for engineering projects is probabilistic seismic-hazard analysis (PSHA). The primary output from a PSHA is a hazard curve showing the variation of a selected ground-motion parameter, such as peak ground acceleration (PGA) or spectral acceleration (SA), against the annual frequency of exceedance (or its reciprocal, return period). The design value is the ground-motion level that corresponds to a preselected design return period. For many engineering projects, such as standard buildings and typical bridges, the seismic loading is taken from the appropriate seismic-design code, the basis of which is usually a PSHA. For more important engineering projects— where the consequences of failure are more serious, such as dams and chemical plants—it is more usual to obtain the seismic-design loads from a site-specific PSHA, in general, using much longer return periods than those governing code based design. Calculation of Probabilistic Seismic Hazard was performed using Software CRISIS2007 by Ordaz, M., Aguilar, A., and Arboleda, J., Instituto de Ingeniería, UNAM, Mexico. CRISIS implements a classical probabilistic seismic hazard methodology where seismic sources can be modelled as points, lines and areas. In the case of area sources, the software offers an integration procedure that takes advantage of a triangulation algorithm used for seismic source discretization. This solution improves calculation efficiency while maintaining a reliable description of source geometry and seismicity. Additionally, supplementary filters (e.g. fix a sitesource distance that excludes from calculation sources at great distance) allow the program to balance precision and efficiency during hazard calculation. Earthquake temporal occurrence is assumed to follow a Poisson process, and the code facilitates two types of MFDs: a truncated exponential Gutenberg-Richter [1944] magnitude distribution and a characteristic magnitude

  10. Data Set From Molisan Regional Seismic Network Events

    CERN Document Server

    De Gasperis, Giovanni

    2016-01-01

    After the earthquake occurred in Molise (Central Italy) on 31st October 2002 (Ml 5.4, 29 people dead), the local Servizio Regionale per la Protezione Civile to ensure a better analysis of local seismic data, through a convention with the Istituto Nazionale di Geofisica e Vulcanologia (INGV), promoted the design of the Regional Seismic Network (RMSM) and funded its implementation. The 5 stations of RMSM worked since 2007 to 2013 collecting a large amount of seismic data and giving an important contribution to the study of seismic sources present in the region and the surrounding territory. This work reports about the dataset containing all triggers collected by RMSM since July 2007 to March 2009, including actual seismic events; among them, all earthquakes events recorded in coincidence to Rete Sismica Nazionale Centralizzata (RSNC) of INGV have been marked with S and P arrival timestamps. Every trigger has been associated to a spectrogram defined into a recorded time vs. frequency domain. The main aim of this...

  11. SEISMIC MODELING ENGINES PHASE 1 FINAL REPORT

    Energy Technology Data Exchange (ETDEWEB)

    BRUCE P. MARION

    2006-02-09

    Seismic modeling is a core component of petroleum exploration and production today. Potential applications include modeling the influence of dip on anisotropic migration; source/receiver placement in deviated-well three-dimensional surveys for vertical seismic profiling (VSP); and the generation of realistic data sets for testing contractor-supplied migration algorithms or for interpreting AVO (amplitude variation with offset) responses. This project was designed to extend the use of a finite-difference modeling package, developed at Lawrence Berkeley Laboratories, to the advanced applications needed by industry. The approach included a realistic, easy-to-use 2-D modeling package for the desktop of the practicing geophysicist. The feasibility of providing a wide-ranging set of seismic modeling engines was fully demonstrated in Phase I. The technical focus was on adding variable gridding in both the horizontal and vertical directions, incorporating attenuation, improving absorbing boundary conditions and adding the optional coefficient finite difference methods.

  12. Automatic interpretation of regional short period seismic signals using CUSUM-SA algorithms

    Science.gov (United States)

    der, Zoltan A.; Shumway, Robert H.

    Several simple methods for the automatic interpretation of short period regional seismogram were tested. Because of the emergent nature of most regional arrivals, the onsets of seismic phases are associated with gradual, rather than sudden, changes in the autoregressive models and mean square amplitudes. We have found that amplitude contrasts between windows containing the seismic phase and the noise (background prior to the arrival) can be enhanced by filtering making use of autoregressive models and thus in the further analysis we utilize only the enhanced amplitude changes for defining onset times.

  13. Seismicity of Czorsztyn Lake Region: A Case of Reservoir Triggered Seismic Process?

    Directory of Open Access Journals (Sweden)

    Białoń Wojciech

    2015-08-01

    Full Text Available Czorsztyn Lake is an artificial water reservoir backed up by the hydropower plant Niedzica earth dam on Dunajec River in south Poland. Its filling began in 1995 and ended in 1997. The reservoir of 234.5 million m3 capacity is shallow, between 20 to 50 m of water column, on average. Until 2011 the seismic activity in this region was sparse, some 1 event trimonthly. However, in November 2011 more than 60 events occurred. Such bursts of activity, separated by low activity periods, continue to appear. Since August 2013 the area is monitored by a local seismic network. The setup allows to accurately locate the epicenters and to determine source mechanisms for stronger events. The events are clustered and aligned along NE-SW direction and their mechanisms are very similar, indicating N-S strike slip faulting. This and the irregular pattern of activity suggest that this seismicity is triggered by the reservoir impoundment

  14. Seismicity, structure and tectonics in the Arctic region

    Directory of Open Access Journals (Sweden)

    Masaki Kanao

    2015-09-01

    Full Text Available The “Arctic” region, where the North Pole occupies the center of the Arctic Ocean, has been affecting the environmental variation of the Earth from geological time to the present. However, the seismic activities in the area are not adequately monitored. Therefore, by conducting long term monitoring of seismic phenomenon as sustainable parameters, our understanding of both the tectonic evolution of the Earth and the dynamic interaction between the cryosphere and geosphere in surface layers of the Earth will increase. In this paper, the association of the seismicity and structure of the Arctic region, particularly focused on Eurasian continent and surrounding oceans, and its relationship with regional evolution during the Earth's history is studied. The target areas cover representative tectonic provinces in the Eurasian Arctic, such as the wide area of Siberia, Baikal Rift Zone, Far East Russia, Arctic Ocean together with Greenland and Northern Canada. Based on discussion including characteristics of seismicity, heterogeneous structure of the crust and upper mantle, tectonic history and recent dynamic features of the Earth's surface in the Arctic are summarized.

  15. Seismicity, structure and tectonics in the Arctic region

    Institute of Scientific and Technical Information of China (English)

    Masaki Kanao; Vladimir D. Suvorov; Shigeru Toda; Seiji Tsuboi

    2015-01-01

    The“Arctic”region, where the North Pole occupies the center of the Arctic Ocean, has been affecting the environmental variation of the Earth from geological time to the present. However, the seismic activities in the area are not adequately monitored. Therefore, by conducting long term monitoring of seismic phenomenon as sustainable parameters, our understanding of both the tectonic evolution of the Earth and the dynamic interaction between the cryosphere and geosphere in surface layers of the Earth will increase. In this paper, the association of the seismicity and structure of the Arctic region, particularly focused on Eurasian continent and surrounding oceans, and its relationship with regional evolution during the Earth’s history is studied. The target areas cover representative tectonic provinces in the Eurasian Arctic, such as the wide area of Siberia, Baikal Rift Zone, Far East Russia, Arctic Ocean together with Greenland and Northern Canada. Based on discussion including characteristics of seismicity, het-erogeneous structure of the crust and upper mantle, tectonic history and recent dynamic features of the Earth’s surface in the Arctic are summarized.

  16. Regional Seismic Focal Depth Estimation in Complex Tectonic Environments

    Science.gov (United States)

    2007-09-01

    seismicity in Iran region, Geophys. J. Int. 167: 761–778. Hatzfeld, D., M. Tatar, K. Priestley, and M. Ghafory-Ashtiany (2003). Seismological constraints...receiver functions and crustal structure. In Computer programs in seismology . Kennett B. L. N., and E. R. Engdahl (1991), Travel times for global...estimation. Proc. RADC Spectral Estimation Workshop, 243–258, Rome, Italy . Stroujkova, A. and D. Reiter (2006). Regional Depth Phase Detection and Focal

  17. Model and observed seismicity represented in a two dimensional space

    Directory of Open Access Journals (Sweden)

    M. Caputo

    1976-06-01

    Full Text Available In recent years theoretical seismology lias introduced
    some formulae relating the magnitude and the seismic moment of earthquakes
    to the size of the fault and the stress drop which generated the
    earthquake.
    In the present paper we introduce a model for the statistics of the
    earthquakes based on these formulae. The model gives formulae which
    show internal consistency and are also confirmed by observations.
    For intermediate magnitudes the formulae reproduce also the trend
    of linearity of the statistics of magnitude and moment observed in all the
    seismic regions of the world. This linear trend changes into a curve with
    increasing slope for large magnitudes and moment.
    When a catalogue of the magnitudes and/or the seismic moment of
    the earthquakes of a seismic region is available, the model allows to estimate
    the maximum magnitude possible in the region.

  18. RELM (the Working Group for the Development of Region Earthquake Likelihood Models) and the Development of new, Open-Source, Java-Based (Object Oriented) Code for Probabilistic Seismic Hazard Analysis

    Science.gov (United States)

    Field, E. H.

    2001-12-01

    Given problems with virtually all previous earthquake-forecast models for southern California, and a current lack of consensus on how such models should be constructed, a joint SCEC-USGS sponsored working group for the development of Regional Earthquake Likelihood Models (RELM) has been established (www.relm.org). The goals are as follows: 1) To develop and test a range of viable earthquake-potential models for southern California (not just one "consensus" model); 2) To examine and compare the implications of each model with respect to probabilistic seismic-hazard estimates (which will not only quantify existing hazard uncertainties, but will also indicate how future research should be focused in order to reduce the uncertainties); and 3) To design and document conclusive tests of each model with respect to existing and future geophysical observations. The variety of models under development reflects the variety of geophysical constraints available; these include geological fault information, historical seismicity, geodetic observations, stress-transfer interactions, and foreshock/aftershock statistics. One reason for developing and testing a range of models is to evaluate the extent to which any one can be exported to another region where the options are more limited. RELM is not intended to be a one-time effort. Rather, we are building an infrastructure that will facilitate an ongoing incorporation of new scientific findings into seismic-hazard models. The effort involves the development of several community models and databases, one of which is new Java-based code for probabilistic seismic hazard analysis (PSHA). Although several different PSHA codes presently exist, none are open source, well documented, and written in an object-oriented programming language (which is ideally suited for PSHA). Furthermore, we need code that is flexible enough to accommodate the wide range of models currently under development in RELM. The new code is being developed under

  19. Seismic monitoring in Namaqualand/Bushmanland region

    CSIR Research Space (South Africa)

    Malephane, H

    2013-10-01

    Full Text Available The Namaqualand-Bushmanland region has numerous features that make it attractive for the storage of radioactive waste. In the late 1970s a programme to find a suitable site for low- and intermediate-level waste was launched and Vaalputs...

  20. Detailed seismic modeling of induced seismicity at the Groningen gas field

    NARCIS (Netherlands)

    Paap, B.F.; Steeghs, T.P.H.; Kraaijpoel, D.A.

    2016-01-01

    We present the results of a detailed seismic modeling study of induced seismicity observed at the Groningen gas field, situated in the North-eastern part of the Netherlands. Seismic simulations are valuable to support the interpretation of observed earthquake waveforms recordings and to increase the

  1. Comparison between seismic and domestic risk in moderate seismic hazard prone region: the Grenoble City (France test site

    Directory of Open Access Journals (Sweden)

    F. Dunand

    2012-02-01

    Full Text Available France has a moderate level of seismic activity, characterized by diffuse seismicity, sometimes experiencing earthquakes of a magnitude of more than 5 in the most active zones. In this seismicity context, Grenoble is a city of major economic and social importance. However, earthquakes being rare, public authorities and the decision makers are only vaguely committed to reducing seismic risk: return periods are long and local policy makers do not have much information available. Over the past 25 yr, a large number of studies have been conducted to improve our knowledge of seismic hazard in this region. One of the decision-making concerns of Grenoble's public authorities, as managers of a large number of public buildings, is to know not only the seismic-prone regions, the variability of seismic hazard due to site effects and the city's overall vulnerability, but also the level of seismic risk and exposure for the entire city, also compared to other natural or/and domestic hazards. Our seismic risk analysis uses a probabilistic approach for regional and local hazards and the vulnerability assessment of buildings. Its applicability to Grenoble offers the advantage of being based on knowledge acquired by previous projects conducted over the years. This paper aims to compare the level of seismic risk with that of other risks and to introduce the notion of risk acceptability in order to offer guidance in the management of seismic risk. This notion of acceptability, which is now part of seismic risk consideration for existing buildings in Switzerland, is relevant in moderately seismic-prone countries like France.

  2. Contribution to the study of historical seismicity in the Maghrebian region, Catalogue of historiacal seismicity of the Maghreb region

    Science.gov (United States)

    Elmrabet, T.

    2009-04-01

    The seismic risk assessment in countries with moderate seismic activity is a very delicate action as well as a high priority one in land use management and urban rehabilitation. The credibility of this assessment is based mainly on the effects of destructive earthquakes whose maximum intensities become a reference for determining the level of protection. This knowledge requires a detailed study of the damage caused by major earthquakes over a long period of time. In this context, a broad scale research about past earthquakes started in the Geophysics Laboratory, now called the National Geophysics Institute (ING) within the National Center for Scientific and Technical Research in Rabat, Morocco. It supported a thorough study which included critical historical texts scattered in various local and foreign archives. The pursuit of this study, under the project called PAMERAR, which was launched in the early 80's aimed at reducing of earthquake risk in the Arab region, led us to investigate the origin of these texts according to various public and private libraries, as in Spain and France. The scientific interest in the historical seismicity in Morocco was highlighted at the beginning of the twentieth century in several reports and catalogs but with several gaps in time and space, further research was thus necessary especially to explore documents in particular from origin sources. This interest in historical archives is within the scope of understanding the natural hazards over long period to evaluate the recurrence of earthquakes. This study leads to significant results covering 11 centuries, from AD 846 to the present. We continued to study the effects of recent earthquakes on humans and buildings heritage, this work has led to a study in the footsteps of local seismic culture. Since earthquakes do not recognize the limits of political geography, since 1993 we have undertaken to extend the research to include the entire Maghreb region. We then used the database

  3. Development and Mechanical Performance of a New Kind of Bridge Seismic Isolator for Low Seismic Regions

    Directory of Open Access Journals (Sweden)

    H. Zhang

    2013-01-01

    Full Text Available The concept of fibre-reinforced plate elastomeric isolator (FRPEI is introduced firstly in this paper. Three FRPEI specimens have been constructed to evaluate the mechanical performance of the isolators by performing vertical and horizontal tests. The research focuses on the compression stiffness, the shear stiffness, the hysteretic characteristic and the vertical bearing capacity of the isolators. The experimental results show that the mechanical performance of FRPEIs can meet the requirements of bridge rubber bearings and the energy dissipation capacity is better than that of general laminated rubber bearings. Therefore, it is feasible to use FRPEIs in seismic isolation of short span bridges in low seismic regions. Theoretical and finite element methods have also been employed and the deformation assumptions applied in the theoretical method are also verified by FEM. By comparing the differences of the results of different methods, the effectivenesses of the theoretical and finite element methods are evaluated and some considerations on isolator design are proposed.

  4. Deep Mantle Seismic Modeling and Imaging

    Science.gov (United States)

    Lay, Thorne; Garnero, Edward J.

    2011-05-01

    Detailed seismic modeling and imaging of Earth's deep interior is providing key information about lower-mantle structures and processes, including heat flow across the core-mantle boundary, the configuration of mantle upwellings and downwellings, phase equilibria and transport properties of deep mantle materials, and mechanisms of core-mantle coupling. Multichannel seismic wave analysis methods that provide the highest-resolution deep mantle structural information include network waveform modeling and stacking, array processing, and 3D migrations of P- and S-wave seismograms. These methods detect and identify weak signals from structures that cannot be resolved by global seismic tomography. Some methods are adapted from oil exploration seismology, but all are constrained by the source and receiver distributions, long travel paths, and strong attenuation experienced by seismic waves that penetrate to the deep mantle. Large- and small-scale structures, with velocity variations ranging from a fraction of a percent to tens of percent, have been detected and are guiding geophysicists to new perspectives of thermochemical mantle convection and evolution.

  5. Neotectonics and seismicity of the Clearlake region in northern California

    Energy Technology Data Exchange (ETDEWEB)

    Burns, K.L.

    1996-04-01

    Geological, topographic, and seismic methods were used to locate faults in the vicinity of Clearlake in northern California. The geological method, which seeks faults as discontinuities in the lithotope, found faults in the Tertiary-Cretaceous rocks east of Burns Valley. The topographic method, which is used to produce Fault Evaluation Reports, found a very active fault zone, the Konocti Bay fault zone, south of Highlands arm. It also found some active faults north of Highlands arm, in the eastern part of Burns Valley and on the lakeshore near Oak Park. The seismic method is the most enduring of the three methods but is limited by location accuracy; the results improve as monitoring continues because of increases in the density of events and improvements in the crustal velocity model. The seismic method identified faulting along the valley at Borax Lake and possibly also on a line running northeast from the city of Clearlake. The latter may be associated with the Burns Valley fault or with the line of scoria domes which runs parallel to it. Seismic observations over longer periods at higher resolution will be required in order to determine the location of active faults near the city. 47 refs., 13 figs.

  6. Assessing the Comprehensive Seismic Earth Model using normal mode data

    Science.gov (United States)

    Koelemeijer, Paula; Afanasiev, Michael; Fichtner, Andreas; Gokhberg, Alexey

    2016-04-01

    Advances in computational resources and numerical methods allow the simulation of realistic seismic wave propagation through complex media, while ensuring that the complete wave field is correctly represented in synthetic seismograms. This full waveform inversion is widely applied on regional and continental scales, where particularly dense data sampled can be achieved leading to an increased resolution in the obtained model images. On a global scale, however, full waveform tomography is still and will continue to be limited to longer length scales due to the large computational costs. Normal mode tomography provides an alternative fast full waveform approach for imaging seismic structures in a global way. Normal modes are not limited by the poor station-earthquake distribution and provide sensitivity to density structure. Using normal modes, a more robust long wavelength background model can be obtained, leading to more accurate absolute velocity models for tectonic and mineral physics interpretations. In addition, it is vital to combine all seismic data types across accessible periods to obtain a more complete, consistent and interpretable image of the Earth's interior. Here, we aim to combine the globally sensitive long period normal modes with shorter period full waveform modelling within the multi-scale framework of the Comprehensive Seismic Earth Model (CSEM). The multi-scale inversion framework of the CSEM allows exploitation of the full waveform capacity on both sides of the seismic spectrum. As the CSEM includes high-resolution subregions with velocity variations at much shorter wavelengths than normal modes could constrain, the question arises whether these small-scale variations are noticeable in normal mode data, and which modes respond in particular. We report here on experiments in which we address these questions. We separately investigate the effects of small-scale variations in shear-wave velocity and compressional wave velocity compared to the

  7. Evaluation of induced seismicity forecast models in the Induced Seismicity Test Bench

    Science.gov (United States)

    Király, Eszter; Gischig, Valentin; Zechar, Jeremy; Doetsch, Joseph; Karvounis, Dimitrios; Wiemer, Stefan

    2016-04-01

    Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. Here, we propose an Induced Seismicity Test Bench to test and rank such models. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models that incorporate a different mix of physical understanding and stochastic representation of the induced sequences: Shapiro in Space (SiS) and Hydraulics and Seismics (HySei). SiS is based on three pillars: the seismicity rate is computed with help of the seismogenic index and a simple exponential decay of the seismicity; the magnitude distribution follows the Gutenberg-Richter relation; and seismicity is distributed in space based on smoothing seismicity during the learning period with 3D Gaussian kernels. The HySei model describes seismicity triggered by pressure diffusion with irreversible permeability enhancement. Our results show that neither model is fully superior to the other. HySei forecasts the seismicity rate well, but is only mediocre at forecasting the spatial distribution. On the other hand, SiS forecasts the spatial distribution well but not the seismicity rate. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in. Ensemble models that combine HySei's rate forecast with SiS's spatial forecast outperform each individual model.

  8. Introducing Seismic Tomography with Computational Modeling

    Science.gov (United States)

    Neves, R.; Neves, M. L.; Teodoro, V.

    2011-12-01

    Learning seismic tomography principles and techniques involves advanced physical and computational knowledge. In depth learning of such computational skills is a difficult cognitive process that requires a strong background in physics, mathematics and computer programming. The corresponding learning environments and pedagogic methodologies should then involve sets of computational modelling activities with computer software systems which allow students the possibility to improve their mathematical or programming knowledge and simultaneously focus on the learning of seismic wave propagation and inverse theory. To reduce the level of cognitive opacity associated with mathematical or programming knowledge, several computer modelling systems have already been developed (Neves & Teodoro, 2010). Among such systems, Modellus is particularly well suited to achieve this goal because it is a domain general environment for explorative and expressive modelling with the following main advantages: 1) an easy and intuitive creation of mathematical models using just standard mathematical notation; 2) the simultaneous exploration of images, tables, graphs and object animations; 3) the attribution of mathematical properties expressed in the models to animated objects; and finally 4) the computation and display of mathematical quantities obtained from the analysis of images and graphs. Here we describe virtual simulations and educational exercises which enable students an easy grasp of the fundamental of seismic tomography. The simulations make the lecture more interactive and allow students the possibility to overcome their lack of advanced mathematical or programming knowledge and focus on the learning of seismological concepts and processes taking advantage of basic scientific computation methods and tools.

  9. The Irpinia Seismic Network (ISN): a new Monitoring Infrastructure for Seismic Alert Management in Campania Region, Southern Italy

    Science.gov (United States)

    Iannaccone, G.; Satriano, C.; Weber, E.; Cantore, L.; Corciulo, M.; Romano, L.; Martino, C.; Dicrosta, M.; Zollo, A.

    2005-12-01

    The Irpinia Seismic Network is an high dynamics, high density seismographic network under development in the Southern Apenninic chain. It is deployed in the area stroken by several destructive earthquakes during last centuries. In its final configuration the network will consist of more than fourty high dynamic seismic stations subdivided in physical subnetworks inter-connected by a robust data transmission system. The system is being designed with two primary targets: -Monitoring and analysis of background seismic activity produced by the active fault system which is the cause for large earthquakes in the past, included the 1980, Irpinia earthquake (Ms=6.9) - Development and experimentation of a prototype system for seismic early and post-event warning to be used for protecting public infrastructures and buildings of strategic relevance of the Regione Campania The seismic network will be completed in two stages: 1 - Deployment of 30 seismic stations along the Campania-Lucania Apenninic chain (to date almost completed) 2 - Setting up radio communication system for data transmission. Installation of 12 additional seismic stations (end of year 2006) To ensure an high dynamic recording range each site is equipped with two type of sensors: 30 force-balance accelerometer (model Guralp CMG5-T) and a velocimeter. In particular, 25 sites with short period three components instrument (model Geotech S13-J) and 5 with broad-band sensor (Nanometrics Trillium, with frequency response in the 0.033-50 Hz band). The used data logger is the Osiris-6 model produced by Agecodagis whose main features are: six channels, O/N 24 bit A/D converter, ARM processor with embedded Linux and open source software, two PCMCIA slots (used for two 5GB microdrive or one disk and wi-fi card), Ethernet, wi-fi and serial communication, low power cosumption (~1 W). Power is ensured by two 120 W solar panels and two 130 Ah gel batteries. Each recording site is equipped with a control/alarm system through

  10. Q Values of Seismic Coda in Ningxia and Adjacent Regions based on Sato Model%利用Sato模型对宁夏及邻区尾波Q值的研究

    Institute of Scientific and Technical Information of China (English)

    师海阔; 朱新运; 贺永忠; 张立恒

    2011-01-01

    Based on the Sato model, adopting digital wave datas of 121 earthquake above ML2.0 from January 2008 to December 2009, which were recorded by Ningxia earthquake nets, the average Q value of seismic coda in relative regions is calculated, and the relationship between Q value and frequency is polyfited. The whole region's result is Q(f)= (44.81±15.87) · f0.9491±0.0805. Compared with other regions, the Q value of seismic coda in Ningxia and adjacent regions is relatively lower, but the dependence on frequency is higher. According to the regional seismic tectonic characteristics and the homochronous seismic activity, we divided the research region into four concentrated minor-earthquake areas: (a) Ji Lantai, (b) Yin Chuan, (c) Wei Ningtong, (d) Gu Hai, and the calculated Q values of the four regions relatively are: (a) Q(f)= (53.59±17.08)f0.9148±0.0692, (b) O(f) = (53.04± 16.29)f0.921±0.0777, (c) Q(f) = (42. 25 ± 15.03)f0.9532±0.0787, (d) Q(f) = (41.65 ± 13.46) f0.9636±0.0774. Comparison of the polyfited results shows that Q value' s distribution reflects the related region's tectonic activities and seismic activity.%本文利用Sato模型,选取2008-2009年宁夏地震台网记录的121次ML≥2.0地震的数字地震波资料,计算宁夏及邻区平均尾波Q值,并拟合了Q值对频率的依赖关系. 结果表明,与国内其他地区相比,宁夏及邻区Q值较低,对频率f依赖性较高. 结合研究区同期地震活动水平及地震地质构造特征,将研究区划分为四个小震密集区:吉兰泰地震区、银川地震区、卫宁同地震区、固海地震区. 分别统计并拟合Q值对频率的关系式为Q(f)=(53.59±17.08)f 0.9148±0.0692;Q(f)=(53.04±16.29)f 0.921±0.0777;Q(f)=(42.25±15.03)f 0.9532±0.0787及Q(f)=(41.65±13.46)f 0.9636±0.0774. 对拟合结果进行比较表明,Q值分布较好地反映了相关构造区构造活动及地震活动水平.

  11. Numerical modeling of tunneling-induced seismicity

    Science.gov (United States)

    Rinaldi, Antonio Pio; Urpi, Luca

    2017-04-01

    Removal of rock mass in mining environment has been associated since long-time with seismic event of magnitude 3 and above, with the potential to cause damage to the infrastructures or even loss of human life. Although with similarities with mining, relatively unknown up to now are seismic events induced by tunneling. However with modern mechanized tunneling techniques, making possible to digging deeper and longer underground infrastructure, the risk is not negligible. As an example, the excavation of the 57km long Gotthard Base Tunnel has been associated more than hundred seismic events, with the largest one having magnitude of ML 2.4, damaging the tunnel infrastructures. For future scenario of deep geological storage of nuclear waste, tunneling will constitute the primary activity during site construction. Hence, it will be crucial to understand the risk associated with the underground construction operation that can reactivate seismogenic features nearby the future location of emplacement tunnels. Here we present numerical simulation aimed at understanding the potential for inducing seismicity during tunnel construction. The stress changes and their evolution during the excavation are evaluated with a finite element solver (FLAC3d). A strain-softening friction model is then used to simulate the occurrence of a sudden slip on a fault zone (if critical conditions for reactivation are reached). We also present a sensitivity analysis of the potential for inducing different seismic events by different tunnel sizes at varying distance from a nearby failure plane, with the final purpose of evaluating safety of a potential nuclear repository site on the short- and long-term.

  12. Self-correcting models driven by seismic strain, moment or energy. Applications to the Italian seismicity

    Science.gov (United States)

    Varini, Elisa; Rotondi, Renata; Basili, Roberto; Barba, Salvatore; Betrò, Bruno

    2013-04-01

    The stress release model (Vere-Jones, 1978) provides a stochastic version of the Reid's elastic-rebound theory, which is commonly accepted as the most feasible physical description of the long-term evolution of the earthquake process. It assumes that the stress X, which governs the state of the system in a region, increases linearly with time at a constant loading rate ? imposed by external tectonic forces until it exceeds the strength of the medium and decreases abruptly generating an earthquake. This hypothesis is formalised by a self-correcting point process with conditional intensity function ?(t | Ht) = exp{α + β[?t - S(t)]}, where Ht is the seismic history up to time t, S(t) is the cumulative stress release due to all the earthquakes up to t and α, β and ? are model parameters. X can be any physical parameter that constitutes a proxy measure of the strength of an earthquake, therefore we propose four possible definitions of X and consequently four versions of the stress release model. Let mw denote the moment magnitude of an earthquake and A be its rupture area. We consider two classical versions of the model: in the former X = 100.75(mw-5.3) is the Benioff strain, in the latter X = 101.5(mw-5.3) is the seismic moment. Then we propose two new versions: the third model is based on seismic energy X = 102.25(mw-5.3)-A, the fourth one on the scaled energy X = 100.75(mw-5.3)-A, as defined by Senatorski (2005, 2012). The rupture area A is evaluated by the Wells and Coppersmith regression with parameters depending on the faulting type of the earthquake. We analyse the Italian historical seismicity on a regional basis by subdividing the Italian territory into eight tectonically-coherent large regions. For each model and region, a fully Bayesian analysis is carried out in order to estimate the posterior distributions of the model parameters. We also deal with the forecast problem by evaluating, for each region, the probability distribution F(t | Hs) of the time t

  13. Citizen Science Seismic Stations for Monitoring Regional and Local Events

    Science.gov (United States)

    Zucca, J. J.; Myers, S.; Srikrishna, D.

    2016-12-01

    The earth has tens of thousands of seismometers installed on its surface or in boreholes that are operated by many organizations for many purposes including the study of earthquakes, volcanos, and nuclear explosions. Although global networks such as the Global Seismic Network and the International Monitoring System do an excellent job of monitoring nuclear test explosions and other seismic events, their thresholds could be lowered with the addition of more stations. In recent years there has been interest in citizen-science approaches to augment government-sponsored monitoring networks (see, for example, Stubbs and Drell, 2013). A modestly-priced seismic station that could be purchased by citizen scientists could enhance regional and local coverage of the GSN, IMS, and other networks if those stations are of high enough quality and distributed optimally. In this paper we present a minimum set of hardware and software specifications that a citizen seismograph station would need in order to add value to global networks. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  14. Regional seismic study of the southern Apennine oil discoveries

    Energy Technology Data Exchange (ETDEWEB)

    Finetti, I.R. [Universita di Trieste (Italy); Del Ben, A. [GEXON International, Trieste (Italy)

    1995-08-01

    Based on interpretation of conspicuous regional detailed seismic data sets collected in several years of scientific and professional geophysical exploration activity, the Authors outline basinal conditions of the source rocks deposition during Mesozoic and successive Cenozoic thrusting deformation of the oil basin of Southern Apennine, Italy. Mainly due to its tectonic complexity, only in the last years in the Southern Apennine have been discovered promising oil fields (i.e. Mt. Alpi, Tempa Rossa and Costa Molina). This thrust belt area is now actively explored with a relevant effort to understand the involved detailed tectonic setting and connected geodynamic process. Also basin evolution and source rock distribution are key aspects for success in the exploration activity. The deformation processes of the Apennine Chain are so severe and complex that it is objectively difficult to understand the occurred evolution only investigating local areas, even if in advanced manner. Indeed, for a correct understanding it is indispensable to regionally extend the tectonic inversion firstly to those areas which were involved in Mesozoic by those extensional processes that control the source rocks deposition of the discovered oil fields. This investigation may also clear out the potential areal extent of the discovered producing zone. Successively, it is necessary to reconstruct the young compressive complex tectonization of the involved thrust belt. The regional seismic exploration shows very clearly that large part of the Ionian Sea represents the southeastward not tectonized continuation of the source rocks area of the oil discoveries, locally known with the name of {open_quotes}Lagonegrese{close_quotes}. Seismic information indicates also that the source rocks deposition is associated with a rift activity occurred in Triassic and pursued with a second phase in Middle Jurassic with the formation of a large graben separating the Apulian Platform from the African Plate.

  15. Erosion Associated with Seismically-Induced Landslides in the Middle Longmen Shan Region, Eastern Tibetan Plateau, China

    Directory of Open Access Journals (Sweden)

    Zhikun Ren

    2017-08-01

    Full Text Available The 2008 Wenchuan earthquake and associated co-seismic landslide was the most recent expression of the rapid deformation and erosion occurring in the eastern Tibetan Plateau. The erosion associated with co-seismic landslides balances the long-term tectonic uplift in the topographic evolution of the region; however, the quantitative relationship between earthquakes, uplift, and erosion is still unknown. In order to quantitatively distinguish the seismically-induced erosion in the total erosion, here, we quantify the Wenchuan earthquake-induced erosion using the digital elevation model (DEM differential method and previously-reported landslide volumes. Our results show that the seismically-induced erosion is comparable with the pre-earthquake short-term erosion. The seismically-induced erosion rate contributes ~50% of the total erosion rate, which suggests that the local topographic evolution of the middle Longmen Shan region may be closely related to tectonic events, such as the 2008 Wenchuan earthquake. We propose that seismically-induced erosion is a very important component of the total erosion, particularly in active orogenic regions. Our results demonstrate that the remote sensing technique of differential DEM provides a powerful tool for evaluating the volume of co-seismic landslides produced in intermountain regions by strong earthquakes.

  16. Deep-rooted “thick skinned” model for the High Atlas Mountains (Morocco. Implications for the seismic Eurasia-Africa plate boundary region

    Directory of Open Access Journals (Sweden)

    Guiraud, M.

    2007-06-01

    Full Text Available Previous crustal models of the High Atlas suppose the existence of a mid-crustal detachment where all the surface thrusts merged and below which the lower crust was continuous. However, both seismic refraction data and gravity modeling detected a jump in crustal thickness between the High Atlas and the northern plains. Here we show that this rapid and vertical jump in the depth of Moho discontinuity suggests that a thrust fault may penetrate the lower crust and offset the Moho (deep-rooted “thick skinned” model. The distribution of Neogene and Quaternary volcanisms along and at the northern part of the High Atlas lineament can be related to the beginning of a partial continental subduction of the West African plate to the north underneath Moroccan microplate. Allowing from the complex problem of the plate boundary in the western zone of the Mediterranean, we propose to interpret the South-Atlasic fault zone as the actual northwestern boundary of the stable part of the African plate rather than the Azores-Gibraltar fault currently used.Los modelos geodinámicos existentes sobre la estructura profunda del alto Atlas suponen la existencia de un despegue medio-cortical donde convergen los cabalgamientos superficiales y bajo el cual la corteza inferior es continua. Los datos de sísmica de refracción y gravimetría, sin embargo, indican la existencia de una discontinuidad en el grosor de la corteza (profundidad del Moho bajo el Alto Atlas. En este artículo ponemos de manifiesto que este salto rápido en la profundidad del Moho puede ser causado por un cabalgamiento que penetra la corteza inferior, desplazando la base de la misma ("deeprooted thick skinned model". La distribución del volcanismo Neógeno y Cuaternario a lo largo de y al norte de la alineación del Alto Atlas pueden estar relacionados con el comienzo de una subducción continental parcial de la placa Africana occidental hacia el norte, bajo la microplaca marroquí. La expresi

  17. Study of Seismic Clusters at Bahía de Banderas Region, Mexico

    Science.gov (United States)

    Nunez-Cornu, F. J.; Rutz-Lopez, M.; Suarez-Plascencia, C.; Trejo-Gomez, E.

    2010-12-01

    Given that the coast in the states of Jalisco and south of the state of Nayarit is located within a region of high seismic potential and also because population is increasing, perhaps motivated by the development of tourism, the Civil Defense authorities of Jalisco and the Centro de Sismología y Volcanología de Occidente-SisVOc of Universidad de Guadalajara started in the year 2000 a joint project to study the seismic risk of the region, including the seismic monitoring of Colima volcano (located between the states of Jalisco and Colima). This work focuses on the study of seismicity in the area of Bahía de Banderas and northern coast of Jalisco. To this end, we perform an analysis of available seismograms to characterize active structures, their relationship to surface morphology, and possible reach of these structures into the shallow parts of the bay. The data used in this work are waveforms recorded during the year 2003 during which the seismograph network spanned the region of study. Our method is based on the identification of seismic clusters or families using cross-correlation of waveforms, earthquake relocation and modeling of fault planes. From an initial data set of 404 earthquakes located during 2003, 96 earthquakes could be related to 17 potentially active continental structures. A modeling of fault planes was possible for 11 of these structures. Subgroups of 7 structures are aligned parallel to the Middle America Trench, a possible consequence of oblique subduction. The magnitudes of earthquakes grouped into families is less than 3.6 (Ml), corresponding to fault dimensions of hundreds of meters.

  18. Local and regional seismic response to injection and production at the Salton Sea geothermal field, southern California

    Science.gov (United States)

    Lajoie, L. J.; Brodsky, E. E.

    2011-12-01

    California hosts both the largest geothermal resource capacity and highest seismicity rate in the nation. With plans to increase geothermal output, and proven earthquake triggering in the vicinity of geothermal power plants worldwide, it is important to determine the local and regional effects of geothermal power production. This study focuses on relating the volume of fluid extracted from and re-injected into wells at the Salton Sea geothermal field (SSGF) in Southern California to local seismicity rate and increased probability of larger events on nearby faults such as the San Andreas and Imperial faults. Seismic data is obtained from the publicly available Advanced National Seismic System (ANSS) catalog and SSGF injection and production data from the State of California Department of Conservation. We identify triggered earthquakes in the catalog by modeling seismicity in a 15km radius around the SSGF according to an Epidemic-Type Aftershock Sequence (ETAS) method. The model seeks to fit the cumulative seismicity curve from our dataset by optimizing five seismic parameters in accordance with Gutenberg-Richter and Omori's law. The modeled curve is then removed from the dataset to isolate the non-ETAS, or production-triggered, signal. We then formulate a constitutive law to relate the seismicity rate to the driving stress (i.e. volumetric strain in the reservoir). Defining the local stressing rate provides a tool for predicting the effects that production has on regional seismicity rates. The largest spike in SSGF net production volume over the past 30 years is accompanied by the one of the largest increases in both seismicity rate and moment release within the geothermal field. This indicates a direct coupling between net fluid production volume (volume extracted minus volume re-injected) and seismicity rate and cumulative seismic moment in the field. Three dimensional plots of hypocentral earthquake locations show that seismicity is concentrated on an

  19. A preliminary regional assessment of earthquake-induced landslide susceptibility for Vrancea Seismic Region

    Science.gov (United States)

    Micu, Mihai; Balteanu, Dan; Ionescu, Constantin; Havenith, Hans; Radulian, Mircea; van Westen, Cees; Damen, Michiel; Jurchescu, Marta

    2015-04-01

    In seismically-active regions, earthquakes may trigger landslides enhancing the short-to-long term slope denudation and sediment delivery and conditioning the general landscape evolution. Co-seismic slope failures present in general a low frequency - high magnitude pattern which should be addressed accordingly by landslide hazard assessment, with respect to the generally more frequent precipitation-triggered landslides. The Vrancea Seismic Region, corresponding to the curvature sector of the Eastern Romanian Carpathians, represents the most active sub-crustal (focal depth > 50 km) earthquake province of Europe. It represents the main seismic energy source throughout Romania with significant transboundary effects recorded as far as Ukraine and Bulgaria. During the last 300 years, the region featured 14 earthquakes with M>7, among which seven events with magnitude above 7.5 and three between 7.7 and 7.9. Apart from the direct damages, the Vrancea earthquakes are also responsible for causing numerous other geohazards, such as ground fracturing, groundwater level disturbances and possible deep-seated landslide occurrences (rock slumps, rock-block slides, rock falls, rock avalanches). The older deep-seated landslides (assumed to have been) triggered by earthquakes usually affect the entire slope profile. They often formed landslide dams strongly influencing the river morphology and representing potential threats (through flash-floods) in case of lake outburst. Despite the large potential of this research issue, the correlation between the region's seismotectonic context and landslide predisposing factors has not yet been entirely understood. Presently, there is a lack of information provided by the geohazards databases of Vrancea that does not allow us to outline the seismic influence on the triggering of slope failures in this region. We only know that the morphology of numerous large, deep-seated and dormant landslides (which can possibly be reactivated in future

  20. Seismic imaging and evaluation of channels modeled by boolean approach

    Energy Technology Data Exchange (ETDEWEB)

    Spinola, M.; Aggio, A. [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

    1999-07-01

    The seismic method attempt to image the subsurface architecture and has been able to significantly contribute to detect areal and vertical changes in rock properties. This work presents a seismic imaging study of channel objects generated using the boolean technique. Three channels having different thicknesses were simulated, using the same width, sinuosity and direction. A velocity model was constructed in order to allow seismic contrasts between the interior of channels and the embedding rock. To examine the seismic response for different channel thicknesses, a 3D ray tracing with a normal incident point survey was performed. The three channels were resolved and the way the seismic could image them was studied. (author)

  1. Full Waveform Seismic Inversion for the Japan Region

    Science.gov (United States)

    Žukauskaitė, Saulė; Steptoe, Hamish; Fichtner, Andreas

    2014-05-01

    We present a seismic tomography model for the Japan archipelago obtained using full waveform inversion and adjoint methods. A high-resolution seismic velocity model is essential for Japan as means to comprehend and characterize the complexity of the tectonic setting, and to further our understanding of earthquake sources and rupture propagation. The study area covers the Japanese islands - an area between 20°-50°N and 130°-160°E - and extends to a maximum depth of 500 km. In virtue of complicated tectonics and resulting high seismicity, dense seismic networks are present in Japan and surrounding countries. We make use of broadband data from three networks - F-net in Japan, BATS in Taiwan, and notably, the National Earthquake Network in South Korea. Due to access difficulties, data from this network had not been used in the preceding tomographic study of the same area. We use >50 carefully selected earthquakes, located within the model area and occurring between 1999 and the present. Magnitudes of the events are restricted to 5≤Mw≤6.9 for a point source approximation to be valid. A spectral-element method is used for forward waveform calculation, which comes with the geometric flexibility of finite-elements method and the accuracy of spectral methods. To quantify differences between the observed and synthetic waveforms, we use time-frequency misfits, which exploit the evolution of the frequency content of the data in time. The sensitivities (Fréchet kernels) are then calculated using adjoint methods. The employed methodology allows us to explain the data of dominant period as low as 10 s. To prevent possible over-fitting of the data, we ensure that final misfits are not lower than those obtained if additional (not yet used) data are incorporated. The final results of this study will contribute to the 'Comprehensive Earth Model' being developed by the Computational Seismology group at ETH, with the aim to represent the snapshot of the current knowledge of

  2. Electric, Magnetic and Ionospheric Survey of Seismically Active Regions with SWARM

    Science.gov (United States)

    Echim, Marius M.; Moldovan, Iren; Voiculescu, Mirela; Balasis, George; Lichtenberger, Janos; Heilig, Balazs; Kovacs, Peter

    2014-05-01

    We present a project devoted to the scientific exploitation of SWARM multi-point measurements of the magnetic and electric field, of the electron temperature and density in the ionosphere. These data provide unique opportunities to study in-situ and remotely the electromagnetic and plasma variability due to ionospheric forcing from above and below. The project "Electric, Magnetic and Ionospheric Survey of Seismically Active Regions with SWARM (EMISSARS)" focus on coordinated studies between SWARM and ground based observatories to survey electromagnetic and ionospheric variability at medium latitudes and look for possible correlations with the seismic activity in central Europe. The project is coordinated by the Institute for Space Sciences (INFLPR-ISS) and the National Institute for Earth Physics (INFP) in Bucharest, Romania. In addition to SWARM data the project benefits from support of dedicated ground based measurements provided by the MEMFIS network coordinated by INFP, the MM100 network of magnetic observatories coordinated by the Geological and Geophysical Institute of Hungary (MFGI) in Budapest. Seismic data are provided by INFP and the European Mediterranean Seismological Center. The mission of the project is to monitor from space and from ground the ionospheric and electromagnetic variability during time intervals prior, during and after seismic activity in (i) the seismic active regions of the central Europe and (ii) in regions unaffected by the seismic activity. The latter will provide reference measurements, free from possible seismogenic signals. The scientific objectives of the project are: (1) Observation of electric, magnetic and ionospheric (electron temperature, density) variability in the ionosphere above or in the close vicinity of seismic active regions, in conjunction with ground based observations from dedicated networks; (2) Investigation of the coupling between the litosphere - atmosphere - ionosphere, during Earthquakes; (3) Quantitative

  3. Utah's Regional/Urban ANSS Seismic Network---Strategies and Tools for Quality Performance

    Science.gov (United States)

    Burlacu, R.; Arabasz, W. J.; Pankow, K. L.; Pechmann, J. C.; Drobeck, D. L.; Moeinvaziri, A.; Roberson, P. M.; Rusho, J. A.

    2007-05-01

    The University of Utah's regional/urban seismic network (224 stations recorded: 39 broadband, 87 strong-motion, 98 short-period) has become a model for locally implementing the Advanced National Seismic System (ANSS) because of successes in integrating weak- and strong-motion recording and in developing an effective real-time earthquake information system. Early achievements included implementing ShakeMap, ShakeCast, point-to- multipoint digital telemetry, and an Earthworm Oracle database, as well as in-situ calibration of all broadband and strong-motion stations and submission of all data and metadata into the IRIS DMC. Regarding quality performance, our experience as a medium-size regional network affirms the fundamental importance of basics such as the following: for data acquisition, deliberate attention to high-quality field installations, signal quality, and computer operations; for operational efficiency, a consistent focus on professional project management and human resources; and for customer service, healthy partnerships---including constant interactions with emergency managers, engineers, public policy-makers, and other stakeholders as part of an effective state earthquake program. (Operational cost efficiencies almost invariably involve trade-offs between personnel costs and the quality of hardware and software.) Software tools that we currently rely on for quality performance include those developed by UUSS (e.g., SAC and shell scripts for estimating local magnitudes) and software developed by other organizations such as: USGS (Earthworm), University of Washington (interactive analysis software), ISTI (SeisNetWatch), and IRIS (PDCC, BUD tools). Although there are many pieces, there is little integration. One of the main challenges we face is the availability of a complete and coherent set of tools for automatic and post-processing to assist in achieving the goals/requirements set forth by ANSS. Taking our own network---and ANSS---to the next level

  4. Investigations on Local Seismic Phases and Modeling of Seismic Signals

    Science.gov (United States)

    1993-10-31

    Brocher, T. M., 1987. Coincident seismic reflection/refraction studies of the continental lithosphere: a global review, Rev. Geophys., 25, 723-742...36.39 Laza 300889 42.105 -07.516 13. 3.7 3.9 35.37 Nazare 310389 39.601 -09.493 25 ? 3.7 3.5 33.35 Camero 2009 87 42.138 - 02.476 05. 3.5 3.6 34.35 Aldea ...used might be accurate enough to describe the global waveforms recorded. NEAR SOURCE SITE EFFECTS EXPECTED AT YUCCA FLAT The map of Paleozoic basement

  5. Verifying the self-affine nature of regional seismicity using nonextensive Tsallis statistics

    CERN Document Server

    Minadakis, G; Stonham, J; Nomicos, C; Eftaxias, K

    2012-01-01

    The aspect of self-affine nature of faulting and fracture is widely documented from the data analysis of both field observations and laboratory experiments. In this direction, Huang and Turcotte have stated that the statistics of regional seismicity could be merely a macroscopic reflection of the physical processes in earthquake source, namely, the activation of a single fault is a reduced self-affine image of regional seismicity. This work verifies the aforementioned proposal. More precisely we show that the population of: (i) the earthquakes that precede of a significant event and occur around its the epicentre, and (ii) the "fracto-electromagnetic earthquakes" that are emerged during the fracture of strong entities distributed along the activated single fault sustaining the system follow the same statistics, namely, the relative cumulative number of earthquakes against magnitude. The analysis is mainly performed by means of a recently introduced nonextensive model for earthquake dynamics which leads to a G...

  6. A first-order seismotectonic regionalization of Mexico for seismic hazard and risk estimation

    Science.gov (United States)

    Zúñiga, F. Ramón; Suárez, Gerardo; Figueroa-Soto, Ángel; Mendoza, Avith

    2017-06-01

    The purpose of this work is to define a seismic regionalization of Mexico for seismic hazard and risk analyses. This seismic regionalization is based on seismic, geologic, and tectonic characteristics. To this end, a seismic catalog was compiled using the more reliable sources available. The catalog was made homogeneous in magnitude in order to avoid the differences in the way this parameter is reported by various agencies. Instead of using a linear regression to converts from m b and M d to M s or M w , using only events for which estimates of both magnitudes are available (i.e., paired data), we used the frequency-magnitude relations relying on the a and b values of the Gutenberg-Richter relation. The seismic regions are divided into three main categories: seismicity associated with the subduction process along the Pacific coast of Mexico, in-slab events within the down-going COC and RIV plates, and crustal seismicity associated to various geologic and tectonic regions. In total, 18 seismic regions were identified and delimited. For each, the a and b values of the Gutenberg-Richter relation were determined using a maximum likelihood estimation. The a and b parameters were repeatedly estimated as a function of time for each region, in order to confirm their reliability and stability. The recurrence times predicted by the resulting Gutenberg-Richter relations obtained are compared with the observed recurrence times of the larger events in each region of both historical and instrumental earthquakes.

  7. Experimental Concepts for Testing Seismic Hazard Models

    Science.gov (United States)

    Marzocchi, W.; Jordan, T. H.

    2015-12-01

    Seismic hazard analysis is the primary interface through which useful information about earthquake rupture and wave propagation is delivered to society. To account for the randomness (aleatory variability) and limited knowledge (epistemic uncertainty) of these natural processes, seismologists must formulate and test hazard models using the concepts of probability. In this presentation, we will address the scientific objections that have been raised over the years against probabilistic seismic hazard analysis (PSHA). Owing to the paucity of observations, we must rely on expert opinion to quantify the epistemic uncertainties of PSHA models (e.g., in the weighting of individual models from logic-tree ensembles of plausible models). The main theoretical issue is a frequentist critique: subjectivity is immeasurable; ergo, PSHA models cannot be objectively tested against data; ergo, they are fundamentally unscientific. We have argued (PNAS, 111, 11973-11978) that the Bayesian subjectivity required for casting epistemic uncertainties can be bridged with the frequentist objectivity needed for pure significance testing through "experimental concepts." An experimental concept specifies collections of data, observed and not yet observed, that are judged to be exchangeable (i.e., with a joint distribution independent of the data ordering) when conditioned on a set of explanatory variables. We illustrate, through concrete examples, experimental concepts useful in the testing of PSHA models for ontological errors in the presence of aleatory variability and epistemic uncertainty. In particular, we describe experimental concepts that lead to exchangeable binary sequences that are statistically independent but not identically distributed, showing how the Bayesian concept of exchangeability generalizes the frequentist concept of experimental repeatability. We also address the issue of testing PSHA models using spatially correlated data.

  8. Crustal seismicity and the earthquake catalog maximum moment magnitudes (Mcmax) in stable continental regions (SCRs): correlation with the seismic velocity of the lithosphere

    Science.gov (United States)

    Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun

    2012-01-01

    A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

  9. Seismic anisotropy of upper mantle in Sichuan and adjacent regions

    Institute of Scientific and Technical Information of China (English)

    CHANG LiJun; WANG ChunYong; DING ZhiFeng

    2008-01-01

    Based on the polarization analysis of teleseismic SKS waveform data recorded at 94 broadband seismic stations in Sichuan and adjacent regions, the SKS fast-wave direction and the delay time between the fast and slow shear waves were determined at each station using the grid searching method of minimum transverse energy and the stacking analysis method, and the image of upper mantle anisotropy was acquired. The fast-wave polarization directions are mainly NW-SE in the study area,NWW-SEE to its northeast and NS to its west. The delay time falls into the interval [0.47 s, 1.68 s]. The spatial variation of the fast-wave directions is similar to the variation of GPS velocity directions. The anisotropic image indicates that the regional tectonic stress field has resulted in deformation and flow of upper mantle material, and made the alignment of upper mantle peridotite lattice parallel to the direction of material deformation. The crust-upper mantle deformation in Sichuan and adjacent regions accords with the mode of vertically coherent deformation. In the eastern Tibetan Plateau, the crustal material was extruded to east or southeast clue to SE traction force of the upper mantle material. The extrusion might be obstructed by a rigid block under the Sichuan Basin and the crust has been deformed. After a long-term accumulation of tectonic strain energy, the accumulative energy suddenly released in Yingxiu town of the Longmenshan region, and Wenchuan Ms8.0 earthquake occurred.

  10. The Complementary Nature of Seismic and Infrasound Technologies in Regional Monitoring (Invited)

    Science.gov (United States)

    Stump, B. W.; Hayward, C.; Park, J.

    2013-12-01

    , there are trade-offs between yield and depth (Mueller-Murphy, 1971, Koper et al., 2008, Chun et al., 2011, Murphy et al., 2013, and Park, 2013). An approach to integrating seismic and infrasound observations and models to constrain near-surface sources offers an opportunity to explore these events more fully. The procedure builds on regional and local seismic source models through moment tensors and uses these results to estimate ground motions directly above the source that can then be coupled to an atmospheric propagation code for investigating the complementary infrasound observations. The coupling from the seismic to the infrasound wavefield is done via the Rayleigh integral and the subsequent wave propagation can exercise any one of the existing atmospheric models. As documented in Arrowsmith et al., 2012, the technique has been successfully applied to the analyses and modeling of the seismic and infrasound data associated with the Circleville, Utah magnitude 4.3 earthquake on 3 January 2011. This exercise illustrates the importance of source mechanism, source depth and surface geology on strength of the subsequent infrasound signal as well as the importance of the atmospheric model at the time of the earthquake.

  11. Modelling earthquake interaction and seismicity statistics

    Science.gov (United States)

    Steacy, S.; Hetherington, A.

    2009-04-01

    The effects of earthquake interaction and fault complexity on seismicity statistics are investigated in a 3D model composed of a number of cellular automata (each representing an individual fault) distributed in a volume. Each automaton is assigned a fractal distribution of strength. Failure occurs when the 3D Coulomb stress on any cell exceeds its strength and stress transfer during simulated earthquake rupture is via nearest-neighbor rules formulated to give realistic stress concentrations. An event continues until all neighboring cells whose stresses exceed their strengths have ruptured and the size of the event is determined from its area and stress drop. Long-range stress interactions are computed following the termination of simulated ruptures using a boundary element code. In practice, these stress perturbations are only computed for events above a certain size (e.g. a threshold length of 10 km) and stresses are updated on nearby structures. Events which occur as a result of these stress interactions are considered to be "triggered" earthquakes and they, in turn, can trigger further seismic activity. The threshold length for computing interaction stresses is a free parameter and hence interaction can be "turned off" by setting this to an unrealistically high value. We consider 3 synthetic fault networks of increasing degrees of complexity - modelled on the North Anatolian fault system, the structures in the San Francisco Bay Area, and the Southern California fault network. We find that the effect of interaction is dramatically different in networks of differing complexity. In the North Anatolian analogue, for example, interaction leads to a decreased number of events, increased b-values, and an increase in recurrence intervals. In the Bay Area model, by contrast, we observe that interaction increases the number of events, decreases the b-values, and has little effect on recurrence intervals. For all networks, we find that interaction can activate mis

  12. Geodynamics, Seismicity, Minerageny and Ecology of Arctic Regions

    Science.gov (United States)

    Kutinov, Y. G.

    The researches of Arctic region is necessary for beginning from delimitation of Arctic. Geographically concept "Arctic" uncertain enough. There is a set of approach to definition of its borders and set the variants of these borders (eternal permafrost, boreal tayga, drifting ice, temperature, etc.). Most correct the point of view of Ecology is realization of Arctic borders on borders of the Arctic geo - depression. Such approach allows to consider in a complex migration of natural substance and polluting substance from orogenes to deep-water hollows of Arctic Ocean. On other hand, it is necessary to take into account natural power flows from zone of Mid-Arctic ridge system at Arctic Ocean to continental land, that is opposition direction process. The certificates of such influence at different levels of Earth's crust already has collected enough (speed of seismic wave on Moho discontinuity; modern vertical movement of Earth's crust; distribution of temperature on depth; structure of basement, etc.). During the last 250 million years the Arctic geo-depression has been developing as an autonomous region with circumpolar zonality, and mass-and-energy transfer in its bowlers as well as shitting of lithospheric plates and expansion of the ocean are caused by rotational forces under conditions of an expanding planet. Four types of geoecological structures have been recorded on the basis of deep structures, position in the over-all structures of regions, place in geological history of its evolution, time of appearance, geodynamic regimes , seismicity, structural-morphological features, specific form of appearance and composition of magmatic and sedimentary formations, compositions of soil, specific metallogenic nature, types of human activity, etc. It is tectonic Segments of Earth, as geoecological global structures; the continental marginal perioceanic zones; the branches of continental marginal perioceanic zones; the mineragenic province. The main criteria of ecological

  13. Thermochemical and phase structure of the D"-Region constrained by 3-D spherical mantle convection and seismic tomography

    Science.gov (United States)

    Wu, B.; Olson, P.

    2011-12-01

    Results of time-dependent 3-D spherical mantle convection simulations with Newtonian rheology, solid-state phase transitions, and multiple composition as well as imposed plate motion back to 120 Ma are compared with observed lower mantle seismic heterogeneity to interpret structure in the D"-region. Synthetic seismic tomography images are created from the simulated temperature, composition, and phase change heterogeneity, which are then compared to the global seismic tomography models in terms of pattern and statistical properties. Several models are found that match the seismic tomography in terms of their RMS variation, Gaussian-like frequency distribution, and spherical harmonic degree-2 pattern for global-scale low velocity and high velocity regions. For these best-fitting models the heat flow at the CMB and the mantle heat flow at the surface are about 13.1 ~ 14.7 TW and 31 TW, respectively, and the Urey ratio is in range of 0.36 ~ 0.58. 3-D mantle convection constrained by plate motion history explains the statistics and the global pattern of lower mantle seismic heterogeneity provided that thermal, chemical and phase change heterogeneity is included in the mantle D"-region, and predicts large temporal and spatial variations in heat transport across the CMB.

  14. Evaluation of Atmospheric Electric Field as Increasing Seismic Activity Indicator on the example of Caucasus Region

    CERN Document Server

    Kachakhidze, M K; Kachakhidze, N K

    2012-01-01

    The present paper deals with reliability of a gradient of atmospheric electric field potential as an indicator of seismic activity increase. With this in view, records of atmospheric electric field potential gradients of Caucasus region for 1953-1992 with respect to periods before average and large earthquakes, which took place in the same time interval, were considered. It is worth to pay attention to the fact that the avalanche-like unstable model of fault formation based on theoretical model of self-generated seismo-electromagnetic oscillations of LAI system explains convincingly spectral succession of electromagnetic emission frequency of the periods preceding earthquakes.

  15. Crustal structure, seismicity and seismotectonics of the Trentino region (Southern Alps, Italy)

    Science.gov (United States)

    Viganò, Alfio; Scafidi, Davide; Martin, Silvana; Spallarossa, Daniele; Froner, Luca; Groaz, Oscar

    2013-04-01

    The Trentino region is located at the junction between the central and eastern Southern Alps (Italy), at the intersection between the Giudicarie, Schio-Vicenza and Valsugana fault systems. This area is characterized by relevant lithological and structural lateral heterogeneities, both at the crustal and lithospheric scales. A low-to-moderate seismicity is located in the upper crust, where faults are seismically active under a dominant compressive with variable strike-slip component regime. Here we study the crustal structure of this portion of the Southern Alps (Adria plate) from interpretation of local earthquake tomography images, in relation with distribution of relocated seismicity and regional tectonic patterns. Local earthquake tomography derives from a set of 476 selected earthquakes in the period 1994-2007, with local magnitudes comprised between 0.8 and 5.3. Hypocenter distribution, and number and quality of manually-repicked phases (6322 P and 5483 S) ensure optimal seismic ray coverage. Original recordings are principally from the Provincia Autonoma di Trento (PAT), that manages the Trentino seismic network since 1981, and from other networks (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - INOGS; Istituto Nazionale di Geofisica e Vulcanologia - INGV; others available via the European Integrated Data Archive). The code HYPOELLIPSE is used to perform initial earthquake relocations. The code VELEST is then used to calculate a new minimum 1-D velocity model, as input for tomography. The 3-D tomographic inversion (V P and V P-V S ratio) is obtained via the code SIMULPS, with the implementation of an accurate shooting ray-tracer. The crustal volume is discretized in order to have a regular grid with a homogenous horizontal spatial resolution of 7.5 km. The resolution in depth varies according to the obtained minimum 1-D velocity model. Reliability and accuracy of results are estimated by analyzing the Resolution Diagonal Elements of the

  16. Probabilistic modeling of caprock leakage from seismic reflection data

    DEFF Research Database (Denmark)

    Zunino, Andrea; Hansen, Thomas Mejer; Bergjofd-Kitterød, Ingjerd

    within the storage complexes. The geological models are built on top of geophysical data such as seismic surveys, geological information and well logs from the reservoir or nearby regions. The risk assessment of CO2 storage requires a careful analysis which accounts for all sources of uncertainty...... is a realization of a geostatistical model generated with the help of geological expert knowledge and available prototype models. Employing a Markov chain Monte Carlo method, we generate many realizations of the geostatistical model consistent with our a priori knowledge (in the form of prototype images, well logs....... However, at present, no well-defined and consistent method for mapping the true uncertainty related to the geophysical data and how that uncertainty affects the overall risk assessment for the potential storage site is available. To properly quantify the uncertainties and to avoid unrealistic...

  17. In-situ measurements of seismic velocities in the San Francisco Bay region...part II

    Science.gov (United States)

    Gibbs, James F.; Fumal, Thomas E.; Borcherdt, Roger D.

    1976-01-01

    Seismic wave velocities (compressional and shear) are important parameters for determining the seismic response characteristics of various geologic units when subjected to strong earthquake ground shaking. Seismic velocities of various units often show a strong correlation with the amounts of damage following large earthquakes and have been used as a basis for certain types of seismic zonation studies. Currently a program is in progress to measure seismic velocities in the San Francisco Bay region at an estimated 150 sites. At each site seismic travel times are measured in drill holes, normally at 2.5-m intervals to a depth of 30 m. Geologic logs are determined from drill hole cuttings, undisturbed samples, and penetrometer samples. The data provide a detailed comparison of geologic and seismic characteristics and provide parameters for estimating strong earthquake ground motions quantitatively at each of the site. A major emphasis of this program is to obtain a detailed comparison of geologic and seismic data on a regional scale for use in seismic zonation. The broad data base available in the San Francisco Bay region suggests using the area as a pilot area for the development of general techniques applicable to other areas.

  18. Ensemble-based conditioning of reservoir models to seismic data

    NARCIS (Netherlands)

    Leeuwenburgh, O.; Brouwer, J.; Trani, M.

    2011-01-01

    While 3D seismic has been the basis for geological model building for a long time, time-lapse seismic has primarily been used in a qualitative manner to assist in monitoring reservoir behavior. With the growing acceptance of assisted history matching methods has come an equally rising interest in in

  19. Ensemble-based conditioning of reservoir models to seismic data

    NARCIS (Netherlands)

    Leeuwenburgh, O.; Brouwer, J.; Trani, M.

    2010-01-01

    While 3D seismic has been the basis for geological model building for a long time, time-lapse seismic has primarily been used in a qualitative manner to assist in monitoring reservoir behavior. With the growing acceptance of assisted history matching methods has come an equally rising interest in in

  20. Imaging the continental lithosphere: Perspectives from global and regional anisotropic seismic tomography

    Science.gov (United States)

    Lebedev, Sergei; Schaeffer, Andrew

    2016-04-01

    Azimuthal seismic anisotropy, the dependence of seismic wave speeds on propagation azimuth, is largely due to fabrics within the Earth's crust and mantle, produced by deformation. It thus provides constraints on the distribution and evolution of deformation within the upper mantle. Lateral variations in isotropic-average seismic velocities reflect variations in the temperature of the rocks at depth. Seismic tomography thus also provides a proxy for lateral changes in the temperature and thickness of the lithosphere. It can map the deep boundaries between tectonic blocks with different properties and age of the lithosphere. Our new global, anisotropic, 3D tomographic models of the upper mantle and the crust are constrained by an unprecedentedly large global dataset of broadband waveform fits (over one million seismograms) and provide improved resolution of the lithosphere at the global scale, compared to other available models. The most prominent high-velocity anomalies, seen down to around 200 km depths, indicate the cold, thick, stable mantle lithosphere beneath Precambrian cratons. The tomography resolves the deep boundaries of the cratons even where they are not exposed and difficult to map at the surface. Our large waveform dataset, with complementary large global networks and high-density regional array data, also produces improved resolution of azimuthal anisotropy patterns, so that regional-scale variations related to lithospheric deformation and mantle flow can be resolved, in particular in densely sampled regions. The depth of the boundary between the cold, rigid lithosphere (preserving ancient, frozen anisotropic fabric) and the rheologically weak asthenosphere (characterized by fabric developed recently) can be inferred from the depth layering of seismic anisotropy and its comparison to the past and present plate motions. Beneath oceans, the lithosphere-asthenosphere boundary (LAB) is defined clearly by the layering of anisotropy, with a dependence on

  1. Seismic modelling and ava analysis of hidrocarbon traps

    OpenAIRE

    Faro Gómez, Ricardo J.

    2011-01-01

    In this study, forward seismic modelling of four geological models with Hydrocarbon (HC) traps were performed by ray tracing method to produce synthetic seismogram of each model. The idea is to identify the Hydrocarbon Indicators (HCI‟s) such as bright spot, flat spot, dim spot and Bottom Simulating Reflector (BSR) in the synthethic seismogram. The modelling was performed in DISCO/FOCUS 5.0 seismic data processing programme. Strong positive and negative reflection amplitudes and some artifact...

  2. DOE program on seismic characterization for regions of interest to CTBT monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Ryall, A.S. [Lawrence Livermore National Lab., CA (United States); Weaver, T.A. [Los Alamos National Lab., NM (United States)

    1995-07-01

    The primary goal of the DOE programs on Geophysical Characterization of (1) the Middle East and North Africa (ME-NA) and (2) Southern Asia (SA) is to provide the Air Force Technical Applications Center (AFRAC) with the analytic tools and knowledge base to permit effective verification of Comprehensive Test Ban Treaty (CTBT) compliance in those regions. The program also aims at using these regionalizations as models for the development of a detailed prescription for seismic calibration and knowledge base compilation in areas where the US has had little or no previous monitoring experience. In any given region, the CTBT seismic monitoring system will depend heavily on a few key arrays and/or three-component stations, and it will be important to know as much as possible about the physical properties of the earth`s crust and upper mantle: (1) in the vicinity of these stations, (2) in areas of potential earthquake activity or commercial blasting in the region containing the stations, and (3) along the propagation path from the sources to the stations. To be able to discriminate between various source types, we will also need to know how well the various event characterization techniques perform when they are transported from one tectonic or geologic environment to another. The Department of Energy`s CMT R&D program plan (DOE, 1994), which includes the ME-NA and SA characterization programs, incorporates an iterative process that combines field experiments, computer modeling and data analysis for the development, testing, evaluation and modification of data processing algorithms as appropriate to achieve specific US monitoring objectives. This process will be applied to seismic event detection, location and identification.

  3. The view of seismic hazard in the Halmahera region

    Science.gov (United States)

    Zulkifli, M.; Rudyanto, Ariska; Sakti, Artadi Pria

    2017-07-01

    Seismic hazard analysis for Halmahera region was conducted using PSHA and DSHA methods. The USGS Harmsen 2007 software was used to run probability calculation for return periods of 500 years 10% probability of exceedance within 50 years age of the building on the condition T = 0, T = 0.2 and T = 1. The results show a maximum PGA value in bedrock (0.15 g - 0.26 g), SA T = 0.2 (0.30 g - 0.53 g) and T = 1 (0.12 g - 0.192 g). The Shakemap software modificated by BMKG 2015 was used to run deterministic calculations with earthquake source scenario form a fault plane with magnitude Mw = 8.1, in depth of 20 km. The results obtained a maximum PGA (0.21 g - 0.44 g) with PGA distribution shaped fault plane trace, nearby areas by fault plane have a maximum PGA and away from the fault plane have a minimum PGA.

  4. The 11 May 2011 Lorca earthquake and the seismicity of the region; El terremoto de Lorca de 11 de mayo de 2011 y la sismicidad de la region

    Energy Technology Data Exchange (ETDEWEB)

    Martinez Solares, J. M.; Cantavella Nadal, J. V.; Canas Rodriguez, L.; Valero Zornosa, J. F.

    2012-07-01

    Lorca 2011 seismic series is described presenting its location parameters and the seismic moment tensor of its main events. We analyse its features by means of the whole seismic sequence temporal and spatial distribution, and we compare it with previous seismic series in the same region. Macro seismic data and PGA values gathered in this area are summarized in this paper. In addition, after a thorough revision of the regional seismicity for both historic and instrumental events, we make some modifications in the seismic catalogue. (Author) 32 refs.

  5. Mantle Convection Models Constrained by Seismic Tomography

    Science.gov (United States)

    Durbin, C. J.; Shahnas, M.; Peltier, W. R.; Woodhouse, J. H.

    2011-12-01

    Although available three dimensional models of the lateral heterogeneity of the mantle, based upon the latest advances in seismic tomographic imaging (e.g. Ritsema et al., 2004, JGR) have provided profound insights into aspects of the mantle general circulation that drives continental drift, the compatibility of the tomography with explicit models of mantle mixing has remained illusive. For example, it remains a significant issue as to whether hydrodynamic models of the mixing process alone are able to reconcile the observed detailed pattern of surface plate velocities or whether explicit account must be taken of elastic fracture processes to account for the observed equipartition of kinetic energy between the poloidal and toroidal components of the surface velocity pattern (e.g. Forte and Peltier, 1987, JGR). It is also an issue as to the significance of the role of mantle chemical heterogeneity in determining the buoyancy distribution that drives mantle flow, especially given the expected importance of the spin transition of iron that onsets in the mid-lower mantle, at least in the ferropericlase component of the mineralogy. In this paper we focus upon the application of data assimilation techniques to the development of a model of mantle mixing that is consistent with a modern three dimensional tomography based model of seismic body wave heterogeneity. Beginning with the simplest possible scenario, that chemical heterogeneity is irrelevant to first order, we employ a three dimensional version of the recently published control volume based convection model of Shahnas and Peltier (2010, JGR) as the basis for the assimilation of a three dimensional density field inferred from our preferred tomography model (Ritsema et al., 2004, JGR). The convection model fully incorporates the dynamical influence of the Olivine-Spinel and Spinel-Perovskite+Magnesiowustite solid-solid phase transformations that bracket the mantle transition zone as well as the recently discovered

  6. Sands modeling constrained by high-resolution seismic data

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In the phase of field evaluation, the changing ofinterwell reservoir may be out of control ifthe geological model was built only on well data due to few existing wells. The uncertainty of the interwell reservoir interpolation based only on well data can be decreased by comprehensive utilization of geological, logging and seismic data, especially by using highly relative seismic properties from 3D seismic data adjusted by well point data to restrict interpolation of geological properties. A 3D-geological model which takes the sand body as the direct modeling object was built through stacking the structure, reservoir and water/oil/gas properties together in 3D space.

  7. Incorporating induced seismicity in the 2014 United States National Seismic Hazard Model: results of the 2014 workshop and sensitivity studies

    Science.gov (United States)

    Petersen, Mark D.; Mueller, Charles S.; Moschetti, Morgan P.; Hoover, Susan M.; Rubinstein, Justin L.; Llenos, Andrea L.; Michael, Andrew J.; Ellsworth, William L.; McGarr, Arthur F.; Holland, Austin A.; Anderson, John G.

    2015-01-01

    The U.S. Geological Survey National Seismic Hazard Model for the conterminous United States was updated in 2014 to account for new methods, input models, and data necessary for assessing the seismic ground shaking hazard from natural (tectonic) earthquakes. The U.S. Geological Survey National Seismic Hazard Model project uses probabilistic seismic hazard analysis to quantify the rate of exceedance for earthquake ground shaking (ground motion). For the 2014 National Seismic Hazard Model assessment, the seismic hazard from potentially induced earthquakes was intentionally not considered because we had not determined how to properly treat these earthquakes for the seismic hazard analysis. The phrases “potentially induced” and “induced” are used interchangeably in this report, however it is acknowledged that this classification is based on circumstantial evidence and scientific judgment. For the 2014 National Seismic Hazard Model update, the potentially induced earthquakes were removed from the NSHM’s earthquake catalog, and the documentation states that we would consider alternative models for including induced seismicity in a future version of the National Seismic Hazard Model. As part of the process of incorporating induced seismicity into the seismic hazard model, we evaluate the sensitivity of the seismic hazard from induced seismicity to five parts of the hazard model: (1) the earthquake catalog, (2) earthquake rates, (3) earthquake locations, (4) earthquake Mmax (maximum magnitude), and (5) earthquake ground motions. We describe alternative input models for each of the five parts that represent differences in scientific opinions on induced seismicity characteristics. In this report, however, we do not weight these input models to come up with a preferred final model. Instead, we present a sensitivity study showing uniform seismic hazard maps obtained by applying the alternative input models for induced seismicity. The final model will be released after

  8. The New Avalanche-Like Stochastic Model for Parameterization of Seismicity and Its Application to the South Sakhalin Island Seismicity

    Directory of Open Access Journals (Sweden)

    M. V. Rodkin

    2012-01-01

    Full Text Available Seismic process is usually considered as an example of occurrence of the regime of self-organizing criticality (SOC. A model of seismic regime as an assemblage of randomly developing episodes of avalanche-like relaxation, occurring at a set of metastable subsystems, can be the alternative of such consideration. The model is defined by two parameters characterizing the scaling hierarchical structure of the geophysical medium and the degree of metastability of subsystems of this medium. In the assemblage, these two parameters define a model b-value. An advantage of such approach consists in a clear physical sense of parameters of the model. The application of the model for parameterization of the seismic regime of the south part of Sakhalin Island is considered. The models of space changeability of the scaling parameter and of temporal changeability of the parameter of metastability are constructed. The anomalous increase of the parameter of metastability was found in connection with the Gornozavodsk and Nevelsk earthquakes. At the present time, high values of this parameter occur in the area of the Poyasok Isthmus. This finding is examined in comparison with other indications of an increase in probability of occurrence of a strong earthquake in the South Sakhalin region.

  9. Wide-angle seismic survey in the trench-outer rise region of the central Japan Trench

    Science.gov (United States)

    Fujie, G.; Kodaira, S.; Iwamaru, H.; Shirai, T.; Dannowski, A.; Thorwart, M.; Grevemeyer, I.; Morgan, J. P.

    2015-12-01

    Dehydration process within the subducting oceanic plate and expelled water from there affect various subduction-zone processes, including arc volcanism and generation of earthquakes. This implies that the degree of hydration within the incoming oceanic plate just prior to subduction might be a key control factor on the regional variations in subduction zone processes like interplate earthquakes and arc volcanism. Recent advances in seismic structure studies in the trench-outer rise region of the Japan Trench have revealed that seismic velocities within the incoming oceanic plate become lower owing to the plate bending-related faulting, suggesting the hydration of the oceanic plate. If the degree of the oceanic plate hydration is one of key factors controlling the regional variations of the interplate earthquakes, the degree of the oceanic plate hydration just prior to subduction is expected to show the along-trench variation because the interplate seismicity in the forearc region of the Japan Trench show along-trench variations. However, we cannot discuss the along-trench variation of the incoming plate structure because seismic structure studies have been confined only to the northern Japan Trench so far.In 2014 and 2015, JAMSTEC and GEOMAR conducted wide-angle seismic surveys in the trench-outer rise region of the central Japan Trench to reveal the detailed seismic structure of the incoming oceanic plate. The western extension of our survey line corresponds to the epicenter of the 2011 M9 Tohoku earthquakes. We deployed 88 Ocean Bottom Seismometers (OBSs) at intervals of 6 km and shot a tuned air-gun array of R/V Kairei at 200 m spacing. In this presentation, we will show the overview of our seismic survey and present seismic structure models obtained by the data of mainly 2014 seismic survey together with the several OBS data from 2015 survey. The preliminary results show P-wave velocity (Vp) within the oceanic crust and mantle decreases toward the trench axis

  10. Complex deformation in the Caucasus region revealed by ambient noise seismic tomography

    Science.gov (United States)

    Legendre, Cédric P.; Tseng, Tai-Lin; Chen, Ying-Nien; Huang, Tzu-Ying; Gung, Yuan-Cheng; Karakhanyan, Arkadiy; Huang, Bor-Shouh

    2017-08-01

    Cross-correlation of 3years of ambient seismic noise recorded at 35 seismic stations deployed in Caucasus region yields hundreds of short-period surface-wave phase-speed dispersion curves on inter-station paths. We inverted these measurements using two techniques to construct tomographic images of the principal geological units of Caucasus. High-resolution isotropic and azimuthally anisotropic phase-velocity maps (at periods between 5 and 20s) and shear-velocity tomographic maps between 5 and 30km are generated. The resulting maps show a velocity dichotomy between the Caucasus region and the surrounding that is interpreted in term of changes in crustal thickness. There is also a strong dichotomy in the anisotropic pattern between the eastern part and the western part of the Caucasus. This difference in both amplitudes and directions of the 2ψ anisotropy is linked to the tectonic regime changes in the region. These observations suggest a good correlation between the tomographic models and the geology of the region. It was also possible to identify the early stage of the indentation of the Arabian Plate into the Eurasian plate, as well as to detect the possible magma chamber responsible for the Javakheti highland.

  11. Variation of Seismic Frequency in the Yunnan Region After the Indonesia Earthquake With Ms 8.7

    Institute of Scientific and Technical Information of China (English)

    Guo Tieshuan; Liu Jie; Zheng Dalin; Peng Keyin

    2007-01-01

    The seismic frequency increased significantly in the Yunnan region after the Indonesia earthquake with MS 8.7 on December 26,2004.This was estimated by analyzing the seismic frequency ratio between the influenced and normal times, the spatial distribution characteristics of the increased seismic frequency, the temporal-spatial distribution and types of seismic swarms.Seismic frequency increased at 71.3% of the statistical sites in the Yunnan area.The maximal increase ratio is 18.2.

  12. Background noise model development for seismic stations of KMA

    Science.gov (United States)

    Jeon, Youngsoo

    2010-05-01

    The background noise recorded at seismometer is exist at any seismic signal due to the natural phenomena of the medium which the signal passed through. Reducing the seismic noise is very important to improve the data quality in seismic studies. But, the most important aspect of reducing seismic noise is to find the appropriate place before installing the seismometer. For this reason, NIMR(National Institution of Meteorological Researches) starts to develop a model of standard background noise for the broadband seismic stations of the KMA(Korea Meteorological Administration) using a continuous data set obtained from 13 broadband stations during the period of 2007 and 2008. We also developed the model using short period seismic data from 10 stations at the year of 2009. The method of Mcmara and Buland(2004) is applied to analyse background noise of Korean Peninsula. The fact that borehole seismometer records show low noise level at frequency range greater than 1 Hz compared with that of records at the surface indicate that the cultural noise of inland Korean Peninsula should be considered to process the seismic data set. Reducing Double Frequency peak also should be regarded because the Korean Peninsula surrounded by the seas from eastern, western and southern part. The development of KMA background model shows that the Peterson model(1993) is not applicable to fit the background noise signal generated from Korean Peninsula.

  13. Integrating fault and seismological data into a probabilistic seismic hazard model for Italy.

    Science.gov (United States)

    Valentini, Alessandro; Visini, Francesco; Pace, Bruno

    2017-04-01

    We present the results of new probabilistic seismic hazard analysis (PSHA) for Italy based on active fault and seismological data. Combining seismic hazard from active fault with distributed seismic sources (where there are no data on active faults) is the backbone of this work. Far away from identifying a best procedure, currently adopted approaches combine active faults and background sources applying a threshold magnitude, generally between 5.5 and 7, over which seismicity is modelled by faults, and under which is modelled by distributed sources or area sources. In our PSHA we (i) apply a new method for the treatment of geologic data of major active faults and (ii) propose a new approach to combine these data with historical seismicity to evaluate PSHA for Italy. Assuming that deformation is concentrated in correspondence of fault, we combine the earthquakes occurrences derived from the geometry and slip rates of the active faults with the earthquakes from the spatially smoothed earthquake sources. In the vicinity of an active fault, the smoothed seismic activity is gradually reduced by a fault-size driven factor. Even if the range and gross spatial distribution of expected accelerations obtained in our work are comparable to the ones obtained through methods applying seismic catalogues and classical zonation models, the main difference is in the detailed spatial pattern of our PSHA model: our model is characterized by spots of more hazardous area, in correspondence of mapped active faults, while the previous models give expected accelerations almost uniformly distributed in large regions. Finally, we investigate the impact due to the earthquake rates derived from two magnitude-frequency distribution (MFD) model for faults on the hazard result and in respect to the contribution of faults versus distributed seismic activity.

  14. Optimised spectral merge of the background model in seismic inversion

    Science.gov (United States)

    White, Roy; Zabihi Naeini, Ehsan

    2017-01-01

    The inversion of seismic reflection data to absolute impedance generates low-frequency deviations around the true impedance if the frequency content of the background impedance model does not merge seamlessly into the spectrum of the inverted seismic data. We present a systematic method of selecting a background model that minimises the mismatch between the background model and the relative impedance obtained by inverting the seismic data at wells. At each well a set of well-log relative impedances is formed by passing the impedance log through a set of zero-phase high-pass filters. The corresponding background models are constructed by passing the impedance log through the complementary zero-phase low-pass filters and a set of seismic relative impedances is computed by inverting the seismic data using these background models. If the inverted seismic data is to merge perfectly with the background model, it should correspond at the well to the well-log relative impedance. This correspondence is the basis of a procedure for finding the optimum combination of background model and inverted seismic data. It is difficult to predict the low-frequency content of inverted seismic data. These low frequencies are affected by the uncertainties in (1) measuring the low-frequency response of the seismic wavelet and (2) knowing how inversion protects the signal-to-noise ratio at low frequencies. Uncertainty (1) becomes acute for broadband seismic data; the low-frequency phase is especially difficult to estimate. Moreover we show that a mismatch of low-frequency phase is a serious source of inversion artefacts. We also show that relative impedance can estimate the low-frequency phase where a well tie cannot. Consequently we include a low-frequency phase shift, applied to the seismic relative impedances, in the search for the best spectral merge. The background models are specified by a low-cut corner frequency and the phase shifts by a phase intercept at zero frequency. A scan of

  15. HRM: HII Region Models

    Science.gov (United States)

    Wenger, Trey V.; Kepley, Amanda K.; Balser, Dana S.

    2017-07-01

    HII Region Models fits HII region models to observed radio recombination line and radio continuum data. The algorithm includes the calculations of departure coefficients to correct for non-LTE effects. HII Region Models has been used to model star formation in the nucleus of IC 342.

  16. Grid-Search Location Methods for Ground-Truth Collection from Local and Regional Seismic Networks

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, C A; Rodi, W; Myers, S C

    2003-07-24

    The objective of this project is to develop improved seismic event location techniques that can be used to generate more and better quality reference events using data from local and regional seismic networks. Their approach is to extend existing methods of multiple-event location with more general models of the errors affecting seismic arrival time data, including picking errors and errors in model-based travel-times (path corrections). Toward this end, they are integrating a grid-search based algorithm for multiple-event location (GMEL) with a new parameterization of travel-time corrections and new kriging method for estimating the correction parameters from observed travel-time residuals. Like several other multiple-event location algorithms, GMEL currently assumes event-independent path corrections and is thus restricted to small event clusters. The new parameterization assumes that travel-time corrections are a function of both the event and station location, and builds in source-receiver reciprocity and correlation between the corrections from proximate paths as constraints. The new kriging method simultaneously interpolates travel-time residuals from multiple stations and events to estimate the correction parameters as functions of position. They are currently developing the algorithmic extensions to GMEL needed to combine the new parameterization and kriging method with the simultaneous location of events. The result will be a multiple-event location method which is applicable to non-clustered, spatially well-distributed events. They are applying the existing components of the new multiple-event location method to a data set of regional and local arrival times from Nevada Test Site (NTS) explosions with known origin parameters. Preliminary results show the feasibility and potential benefits of combining the location and kriging techniques. They also show some preliminary work on generalizing of the error model used in GMEL with the use of mixture

  17. Seismically integrated geologic modelling: Guntong Field, Malay Basin

    Energy Technology Data Exchange (ETDEWEB)

    Calvert, Craig S.; Bhuyan, K.; Sterling, J. Helwick; Hill, Rob E.; Hubbard, R. Scott; Khare, Vijay; Wahrmund, Leslie A.; Wang, Gann-Shyong

    1998-12-31

    This presentation relates to a research project on offshore seismically reservoir modelling. The goal of the project was to develop and test a process for interpreting reservoir properties from 3-D seismic data and for integrating these data into the building of 3-D geologic models that would be suitable for use in flow simulation studies. The project produced a 3-D geologic model for three reservoir intervals and three predominantly non-reservoir intervals. Each reservoir interval was subdivided into faces that were determined by integrating core, well log, and seismic interpretations. predictions of porosity and lithology used in building the geologic model were made using seismic attributes calculated from acoustic impedance data. 8 figs.

  18. Multi scale seismic data correlation and integration with regional tectonic framework: example of the Piratininga Dome, SP, Brazil; Correlacao de dados sismicos multiescala e integracao com arcabouco tectonico regional: exemplo da area do Domo de Piratininga, SP

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Adriane Fatima de; Bartoszeck, Marcelo Kulevicz [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Programa de Pos-Graduacao em Geologia. Lab. de Analise de Bacias e Petrofisica]. E-mail: adrianefcampos@yahoo.com.br; Rostirolla, Sidnei Pires; Ferreira, Francisco Jose Fonseca; Romeiro, Marco Antonio Thoaldo [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Geologia; Kiang, Chang Hung [UNESP, Rio Claro, SP (Brazil). Dept. de Geologia Aplicada

    2008-06-15

    The study area covers the Piratininga Dome, a structural high composed by a center horst bordered by faults. The main objective of this work was to establish a systematic multi scale approach, in which high resolution seismic data was compared to conventional seismic, digital terrain models and geophysical potential data. The subsurface data include an 80 km conventional seismic section and the well 1-80 km-1-SP. The Kingdom (Seismic Micro-Technology) software was used to interpret the seismic data in order to map the main horizons and faults. To test the multi scale hypothesis was acquired a high resolution seismic line just over the regional seismic trace. This detailed line measures 1 km length and 360 m depth. The seismic processing was based on a conventional flowchart for CDP technique with Vista (Gedco) software. Shuttle Radar Topography Mission (SRTM) and aero magnetic data of Botucatu and Bauru projects were used to the lineaments interpretation. Comparison between observed horizons in the high resolution and conventional seismic lines made possible to test different alternatives to map structural and stratigraphic features. The obtained multi scale geological elements hierarchies enlarge the knowledge in reservoir resolution. The results of the interpretation indicate the close relationship between regional structural framework and features observed in seismic data, and can be applied to enhance and guide the studies of analogous to depth reservoirs. (author)

  19. Moment Tensor Inversion Using the Kiwi Tools: Application to Regional Seismicity in Portugal

    Science.gov (United States)

    Custodio, Susana; Cesca, Simone; Domingues, Ana

    2010-05-01

    Automatic moment tensor inversions have been applied to earthquakes worldwide since the early 1980s. Since then many techniques have been developed and implemented to perform moment tensor inversions of earthquakes at different scales and in different regions. These inversions typically yield the focal mechanism, magnitude and hypocentral depth of the earthquakes. In some cases, the centroid location is also determined. The finite source of earthquakes has also been studied using several methods. However, fewer attempts have been carried out so far, in order to quickly and automatically determinate extended source parameters. In this presentation we will focus on the adoption of a recently developed inversion method to perform point and kinematic source inversions at regional distances, and its application to regional seismicity recorded in Portugal and neighboring regions. The algorithm works in different steps. At first, we assume a point source approximation. We initially retrieve the focal mechanism of the earthquake (strike, dip, and rake), the seismic scalar moment M0 and the depth. This inversion step is performed in the spectral domain, by fitting amplitude spectra. Since compressive and dilatation quadrants are not distinguishable, this information is retrieved during the second step, which is carried out in the time domain. Refined latitude and longitude for the centroid, as well as an earthquake origin time, can be also retrieved at this time. The final step of the inversion consists of a simplified finite-fault inversion. We assume the recently proposed eikonal source model, and determine parameters such as the fault plane orientation (discrimination between fault and auxiliary plane), radius (rupture extension), nucleation point coordinates (indicative of directivity effects) and average rupture velocity of the earthquake. This inversion is performed in the spectral domain, including higher frequency during the fitting process, and using a grid walk

  20. New GMP Models for Caucasus Region

    Science.gov (United States)

    Jorjiashvili, N.; Godoladze, T.; Tvaradze, N.; Tumanova, N.

    2014-12-01

    The Caucasus is a region of numerous natural hazards and ensuing disasters. Analysis of the losses due to past disasters indicates those most catastrophic in the region have historically been due to strong earthquakes. Estimation of expected ground motion is a fundamental earthquake hazard assessment. The most commonly used parameter for attenuation relation is peak ground acceleration because this parameter gives useful information for Seismic Hazard Assessment. Thus, many peak ground acceleration attenuation relations have been developed by different authors. However, a few attenuation relations were developed for Caucasus region: Ambraseys et al. (1996,2005) which were based on entire European region and they were not focused locally on Caucasus Region, Smit et.al.(2000) that was based on a small amount of acceleration data that really is not enough. Since 2003 construction of Georgian Digital Seismic Network has started with the help of number of International organizations, Projects and Private companies. In this study new GMP models are obtained based on new data from Georgian seismic network and also from neighboring countries. Estimation of models is obtained by classical, statistical way, regression analysis. Also site ground conditions are considered because the same earthquake recorded at the same distance may cause different damage according to ground conditions. Thus, this parameter is emphasized in the present study. Here it must be mentioned that in previous model which only one was done for Caucasus Region (Smit et. al., 2000) local conditions were not considered. Thus, it is an advantage of models from this study.

  1. Seismicity characterization of the Maravatío-Acambay and Actopan regions, central Mexico

    Science.gov (United States)

    Rodríguez-Pérez, Quetzalcoatl; Zúñiga, F. Ramón

    2017-07-01

    We studied the seismic activity in the Maravatío-Acambay and Actopan regions in Central Mexico. These regions are of great importance due to the occurrence of shallow crustal normal-faulting earthquakes that caused widespread destruction near their epicenter and as far away as Mexico City. That was the case of the 19 November 1912 Acambay (Mw 6.9). We determined statistical seismicity characteristics such as the Båth's law (the size of largest aftershock with respect to that of the mainshock), the b-value and p-value. For the Maravatío aftershock sequence, we obtained a b-value of 0.88 and p-value of 0.68. Based on reported seismicity, we obtained a b-value of 1.12 for the Actopan region. We estimated the size of the largest aftershock of the Acambay event in the range of 4.7 size of fragments showed that more energy is released for the Maravatío aftershock sequence than for the regular seismicity rate in the Acambay region. Finally, we analyzed the relation of the seismicity and the tectonic environment by quantifying the seismic coupling and the thickness of the seismogenic layer. The estimated seismogenic layer for the Maravatío-Acambay and Actopan regions are 14.6 km and 20.8 km, respectively. The seismic coupling coefficient at the Venta the Bravo fault in the Maravatío-Acambay region and Actopan region are 0.21 and 0.46, respectively. Our estimation of the seismic coupling coefficients shows that the regions can be classified as low-to-intermediate-coupling zones.

  2. Relocating Seismicity on the Arctic Plate Boundary Using Teleseismic and Regional Phases and a Bayesian Multiple Event Locator

    Science.gov (United States)

    Gibbons, Steven J.; Dahl-Jensen, Trine; Kværna, Tormod; Larsen, Tine B.; Paulsen, Berit; Voss, Peter

    2016-04-01

    The tectonophysics of plate boundaries are illuminated by the pattern of seismicity - and the ability to locate seismic events accurately depends upon the number and quality of observations, the distribution of recording stations, and how well the traveltimes of seismic phases are modelled. The boundary between the Eurasian and North American plates between 70 and 84 degrees North hosts large seismic events which are well recorded teleseismically and many more events at far lower magnitudes that are well recorded only at regional distances. Existing seismic bulletins have considerable spread and bias resulting from limited station coverage and deficiencies in the velocity models applied; this is particularly acute for the lower magnitude events which may only be constrained by a small number of Pn and Sn arrivals. Over the past 15 years, there has been a significant improvement in the seismic network in the Arctic - a difficult region to instrument due to the harsh climate, a sparsity of quiet and accessible sites, and the expense and difficult logistics of deploying and maintaining stations. New deployments and upgrades to stations on Greenland, Svalbard, and the islands Jan Mayen, Hopen, and Bjørnøya have resulted in a sparse but stable regional seismic network which results in events down to magnitudes below 3 generating high quality Pn and Sn signals on multiple stations. A catalog of over 1000 events in the region since 1998 has been generated using many new phase readings on stations on both sides of the spreading ridge in addition to teleseismic P phases. The Bayesloc program, a Bayesian hierarchical multiple event location algorithm, has been used to relocate the full set of events iteratively and this has resulted in a significant reduction in the spread in hypocenter estimates for both large and small events. Whereas single event location algorithms minimize the vector of time residuals on an event-by-event basis, Bayesloc favours the hypocenters which

  3. The attenuation of seismic intensity in the Etna region and comparison with other Italian volcanic districts

    Directory of Open Access Journals (Sweden)

    T. Tuvè

    2006-06-01

    Full Text Available A detailed analysis of the intensity attenuation in the Etna and other Italian volcanic districts, was performed using the most recent and complete intensity datasets. Attenuation laws were derived through empirical models fitting ?I (the difference between epicentral I0 and site Ix intensities average values versus hypocentral site distances by the least-square method. The huge amount of data available for the Etna area allowed us to elaborate bi-linear and logarithmic attenuation models, also taking source effects into account. Furthermore, the coefficients of the Grandori formulation have been re-calculated to verify the ones previously defined for seismic hazard purposes. Among the tested relationships, the logarithmic one is simple and fairly stable, so it was also adopted for the other volcanic Italian areas. The analysis showed different attenuation trends: on the one hand, Etna and Ischia show the highest decay of intensity (?I=4 in the first 20 km; on the contrary, the Aeolian Islands and Albani Hills present a slight intensity attenuation (?I=2 at 20 km from the hypocentre; finally, Vesuvius seems to have an intermediate behaviour between the two groups. The proposed regionalization gives a significantly better image of near-field damage in volcanic regions and is easily applicable to probabilistic seismic hazard analyses.

  4. Tomography and Methods of Travel-Time Calculation for Regional Seismic Location

    Energy Technology Data Exchange (ETDEWEB)

    Myers, S; Ballard, S; Rowe, C; Wagoner, G; Antolik, M; Phillips, S; Ramirez, A; Begnaud, M; Pasyanos, M E; Dodge, D A; Flanagan, M P; Hutchenson, K; Barker, G; Dwyer, J; Russell, D

    2007-07-02

    We are developing a laterally variable velocity model of the crust and upper mantle across Eurasia and North Africa to reduce event location error by improving regional travel-time prediction accuracy. The model includes both P and S velocities and we describe methods to compute travel-times for Pn, Sn, Pg, and Lg phases. For crustal phases Pg and Lg we assume that the waves travel laterally at mid-crustal depths, with added ray segments from the event and station to the mid crustal layer. Our work on Pn and Sn travel-times extends the methods described by Zhao and Xie (1993). With consideration for a continent scale model and application to seismic location, we extend the model parameterization of Zhao and Xie (1993) by allowing the upper-mantle velocity gradient to vary laterally. This extension is needed to accommodate the large variation in gradient that is known to exist across Eurasia and North African. Further, we extend the linear travel-time calculation method to mantle-depth events, which is needed for seismic locators that test many epicenters and depths. Using these methods, regional travel times are computed on-the-fly from the velocity model in milliseconds, forming the basis of a flexible travel time facility that may be implemented in an interactive locator. We use a tomographic technique to improve upon a laterally variable starting velocity model that is based on Lawrence Livermore and Los Alamos National Laboratory model compilation efforts. Our tomographic data set consists of approximately 50 million regional arrivals from events that meet the ground truth (GT) criteria of Bondar et al. (2004) and other non-seismic constraints. Each datum is tested to meet strict quality control standards that include comparison with established distance-dependent travel-time residual populations relative to the IASPIE91 model. In addition to bulletin measurements, nearly 50 thousand arrival measurements were made at the national laboratories. The tomographic

  5. Structure classification from the joint interpretation of seismic and magnetotelluric models

    Science.gov (United States)

    Bedrosian, P. A.; Maercklin, N.; Ritter, O.; Ryberg, T.; Weckmann, U.

    2004-12-01

    Magnetotelluric (MT) and seismic methods provide information about the conductivity and velocity structure of the subsurface on similar scales and resolutions. The independent electrical and seismic tomograms can be combined, using a classification approach, to map lithologic, tectonic, and hydrologic boundaries. The method employed is independent of theoretical/empirical relations linking electrical and seismic parameters, and based solely on the statistical correlation of physical property models in parameter space. Regions of high correlation (classes) can in turn be examined in the spatial domain. The spatial distribution of these clusters, and the boundaries between them, provide structural information not always evident from the individual models. The method is applied to coincident seismic velocity and electrical resistivity models from two active transform margins. Along the San Andreas Fault, classification studies reveal the strong lithological contrast across the fault, suggesting it is sub-vertical in the upper crust throughout central California. A possible hydrologic boundary is further identified to the northeast of the fault. Classification studies along the Dead Sea Transform reflect the dominant lithologies surrounding the fault, and suggest the fault is again vertical in the upper crust, but offset to the east of the surface trace. There are indications that the basement is uplifted by ˜ 2 km east of the fault. These results suggest a quantitative, joint interpretation of MT and seismic data can greatly improve our ability to delineate lithologic, tectonic, and hydrologic boundaries, thus overcoming some of the resolution limitations inherent to the MT and seismic methods.

  6. Joint analysis of the seismic data and velocity gravity model

    Science.gov (United States)

    Belyakov, A. S.; Lavrov, V. S.; Muchamedov, V. A.; Nikolaev, A. V.

    2016-03-01

    We performed joint analysis of the seismic noises recorded at the Japanese Ogasawara station located on Titijima Island in the Philippine Sea using the STS-2 seismograph at the OSW station in the winter period of January 1-15, 2015, over the background of a velocity gravity model. The graphs prove the existence of a cause-and-effect relation between the seismic noise and gravity and allow us to consider it as a desired signal.

  7. Velocity Structure Determination Through Seismic Waveform Modeling and Time Deviations

    Science.gov (United States)

    Savage, B.; Zhu, L.; Tan, Y.; Helmberger, D. V.

    2001-12-01

    Through the use of seismic waveforms recorded by TriNet, a dataset of earthquake focal mechanisms and deviations (time shifts) relative to a standard model facilitates the investigation of the crust and uppermost mantle of southern California. The CAP method of focal mechanism determination, in use by TriNet on a routine basis, provides time shifts for surface waves and Pnl arrivals independently relative to the reference model. These shifts serve as initial data for calibration of local and regional seismic paths. Time shifts from the CAP method are derived by splitting the Pnl section of the waveform, the first arriving Pn to just before the arrival of the S wave, from the much slower surface waves then cross-correlating the data with synthetic waveforms computed from a standard model. Surface waves interact with the entire crust, but the upper crust causes the greatest effect. Whereas, Pnl arrivals sample the deeper crust, upper mantle, and source region. This natural division separates the upper from lower crust for regional calibration and structural modeling and allows 3-D velocity maps to be created using the resulting time shifts. Further examination of Pnl and other arrivals which interact with the Moho illuminate the complex nature of this boundary. Initial attempts at using the first 10 seconds of the Pnl section to determine upper most mantle structure have proven insightful. Two large earthquakes north of southern California in Nevada and Mammoth Lakes, CA allow the creation of record sections from 200 to 600 km. As the paths swing from east to west across southern California, simple 1-D models turn into complex structure, dramatically changing the waveform character. Using finite difference models to explain the structure, we determine that a low velocity zone is present at the base of the crust and extends to 100 km in depth. Velocity variations of 5 percent of the mantle in combination with steeply sloping edges produces complex waveform variations

  8. Seismic velocity structure and seismotectonics of the eastern San Francisco Bay region, California

    Science.gov (United States)

    Hardebeck, J.L.; Michael, A.J.; Brocher, T.M.

    2007-01-01

    The Hayward Fault System is considered the most likely fault system in the San Francisco Bay Area, California, to produce a major earthquake in the next 30 years. To better understand this fault system, we use microseismicity to study its structure and kinematics. We present a new 3D seismic-velocity model for the eastern San Francisco Bay region, using microseismicity and controlled sources, which reveals a ???10% velocity contrast across the Hayward fault in the upper 10 km, with higher velocity in the Franciscan Complex to the west relative to the Great Valley Sequence to the east. This contrast is imaged more sharply in our localized model than in previous regional-scale models. Thick Cenozoic sedimentary basins, such as the Livermore basin, which may experience particularly strong shaking during an earthquake, are imaged in the model. The accurate earthquake locations and focal mechanisms obtained by using the 3D model allow us to study fault complexity and its implications for seismic hazard. The relocated hypocenters along the Hayward Fault in general are consistent with a near-vertical or steeply east-dipping fault zone. The southern Hayward fault merges smoothly with the Calaveras fault at depth, suggesting that large earthquakes may rupture across both faults. The use of the 3D velocity model reveals that most earthquakes along the Hayward fault have near-vertical strike-slip focal mechanisms, consistent with the large-scale orientation and sense of slip of the fault, with no evidence for zones of complex fracturing acting as barriers to earthquake rupture.

  9. 利用两种模型对宁夏及邻区尾波 Q 值进行对比研究%CONTRAST AND RESEARCH ON Q VALUE OF SEISMIC CODA IN NINGXIA AND ADJACENT REGIONS WITH TWO MODELS

    Institute of Scientific and Technical Information of China (English)

    贺永忠; 师海阔; 朱新运; 张立恒

    2012-01-01

    With the Aki model and the Sato model separately, adopting digital earthquake wave datas above ML 2. 0 from January ,2008 to December,2009, which was recorded by Ningxia earthquake nets, the average Q value of seismic coda in relative regions is calculated, and the relation between Q value and frequency is simulated. The results are as follows; with the Aki model:Q(f) = (212 ±87. 62)f0.7584±0.19, the Sato model:Q(f) = (44. 81 ± 15. 87 )f0.9491±±0.0805. Compared with other domestic regions, the results with both of the two models show that the Q value of seismic coda is relatively lower, but the dependence on frequency is higher. So it is considered that the tectonic activity and seismicity are rather high in this region. The Q values in different areas are related with geologic tectonic, and reflect seismicity' s features of the corresponding regions. Results of the two models are comparatively identical, it is considered that the two models are both fit for the research on the Q value of seismic coda in Ningxia and adjacent regions.%分别利用Aki模型和Sato模型,选取2008年1月-2009年12月宁夏地震台网记录的ML≥2.0地震的数字地震波资料,计算了宁夏及邻区平均尾波Q值,并拟合了Q值对频率的依赖关系.结果为:Aki模型为Q(f)=(212±87.62)f0.7584±0.19;Sato模型为Q(f)=(44.81±15.87)f0.9491±0.0805.与国内其他区域相比,两种模型计算结果均显示本区域Q值较低,对频率依赖性较高.研究结果认为两种模型均适合对宁夏及邻区尾波Q值的研究.

  10. Assessing a 3D smoothed seismicity model of induced earthquakes

    Science.gov (United States)

    Zechar, Jeremy; Király, Eszter; Gischig, Valentin; Wiemer, Stefan

    2016-04-01

    As more energy exploration and extraction efforts cause earthquakes, it becomes increasingly important to control induced seismicity. Risk management schemes must be improved and should ultimately be based on near-real-time forecasting systems. With this goal in mind, we propose a test bench to evaluate models of induced seismicity based on metrics developed by the CSEP community. To illustrate the test bench, we consider a model based on the so-called seismogenic index and a rate decay; to produce three-dimensional forecasts, we smooth past earthquakes in space and time. We explore four variants of this model using the Basel 2006 and Soultz-sous-Forêts 2004 datasets to make short-term forecasts, test their consistency, and rank the model variants. Our results suggest that such a smoothed seismicity model is useful for forecasting induced seismicity within three days, and giving more weight to recent events improves forecast performance. Moreover, the location of the largest induced earthquake is forecast well by this model. Despite the good spatial performance, the model does not estimate the seismicity rate well: it frequently overestimates during stimulation and during the early post-stimulation period, and it systematically underestimates around shut-in. In this presentation, we also describe a robust estimate of information gain, a modification that can also benefit forecast experiments involving tectonic earthquakes.

  11. Application of Regional Arrays in Seismic Verification Research

    Science.gov (United States)

    1990-08-31

    world , and the arrays were gener- ally designed for optimum detection capabilities for events at teleseismic distances. The most ambitious...composed of gneisses and gabbro . A seismic reflection profile running north-south slightly east of the array center showed strong in- dications of a...sensors are deployed on gabbro , which is mostly exposed since the soil cover is nonexistent or very thin (up to 0.5 in). The short period seismometers

  12. Renormalization of the ETAS branching model of triggered seismicity from total to observable seismicity

    CERN Document Server

    Saichev, A

    2005-01-01

    Several recent works point out that the crowd of small unobservable earthquakes (with magnitudes below the detection threshold $m_d$) may play a significant and perhaps dominant role in triggering future seismicity. Using the ETAS branching model of triggered seismicity, we apply the formalism of generating probability functions to investigate how the statistical properties of observable earthquakes differ from the statistics of all events. The ETAS (epidemic-type aftershock sequence) model assumes that each earthquake can trigger other earthquakes (``aftershocks''). An aftershock sequence results in this model from the cascade of aftershocks of each past earthquake. The triggering efficiency of earthquakes is assumed to vanish below a lower magnitude limit $m_0$, in order to ensure the convergence of the theory and may reflect the physics of state-and-velocity frictional rupture. We show that, to a good approximation, the ETAS model is renormalized onto itself under what amounts to a decimation procedure $m_...

  13. Numerical simulation of roadbed slope under seismic action in permafrost regions

    Institute of Scientific and Technical Information of China (English)

    JingYu Liu; JianKun Liu; ZhongQin Su; Li Liu; Min Xie

    2013-01-01

    The deformation and strength characteristics of roadbed slope under seismic loading in permafrost regions are simulated numerically. The seismic response of roadbed at different positions and inclinations of a slope section was analyzed. Results show that, roadbed slope damage is mainly led by lateral displacement, and the deformation gradually decreases with increasing depth;roadbed and foundation displacement and plastic strain increases with the magnitude of slope angle, hence the roadbed safety factor will be reduced.

  14. Seismicity studies in the region of the Cerro Prieto Geothermal Field

    Energy Technology Data Exchange (ETDEWEB)

    Albores, A.; Reyes, A.; Brune, J.N.; Gonzalez, J.; Garcilazo, L.; Suarez, F.

    1980-01-01

    This paper reports results from seismicity studies in the region of the Cerro Prieto geothermal field. These studies were conducted with local short period seismic arrays during 1974-1975 and 1977-1978. During the latter period, horizontal seismometers were used for better control on the S-wave arrival times. Locations were obtained for about 200 events and composite fault plane solutions were obtained for five groups of events. 16 refs.

  15. The relationship between seismic velocity structure and the seismic coupling in the Hyuga-nada region, southwest Japan, deduced from onshore and offshore seismic observations

    Science.gov (United States)

    Uehira, K.; Yakiwara, H.; Yamada, T.; Umakoshi, K.; Nakao, S.; Kobayashi, R.; Goto, K.; Miyamachi, H.; Mochizuki, K.; Nakahigashi, K.; Shinohara, M.; Kanazawa, T.; Hino, R.; Goda, M.; Shimizu, H.

    2011-12-01

    In Hyuga-nada region, the Philippine Sea (PHS) plate is subducting beneath the Eurasian (EU) plate (the southwest Japan arc) along the Nankai trough at a rate of about 5 cm per year. Big earthquakes (M7 class) have occurred in the north region from latitude 31.6 degrees north, but it has not occurred in the south region from latitude 31.6 degrees north. The largest earthquake ever recorded in Hyuga-nada region is the 1968 Hyuga-nada earthquake (Mw 7.5). And microseismicity varies spatially. There are non-seismic slip events in Hyuga-nada region. For example, the after-slips associated with events for 19 October 1996 and 3 December 1996 were observed (Yagi et al., 2001), and in the same region, the slow-slip events were also observed by GPS measurements (GSI, 2011). We performed extraordinary seismic observations for 75 days from April to July 2006, for 73 days from April to July 2008, and for 77 days from April to July 2009. About 25 pop-up type ocean-bottom seismometers were deployed above hypocentral region in Hyuga-nada using Nagasaki-maru. And three data loggers were deployed on land in order to compensate a regular seismic network. We used these data and permanent stations for this analysis. In order to obtain precise hypocenter distribution, focal mechanisms, and a 3D seismic velocity structure around the Hyuga-nada region, we used Double-Difference (DD) Tomography method developed by Zhang and Thurber (2003). In northern part of Hyuga-nada, Vp/Vs ratio is high along the upper part of PHS slab, and this layer is interpreted as the subducting oceanic crust. On the other hand, Vp/Vs ratio is about 1.73 in southern part of Hyuga-nada, and this is interpreted as the subducted Kyushu-Palau Ridge, old island arc, which is made by granitic rock. More over, there is a difference of Poisson's ratio at mantle wedge. This value is high (> 0.3) in northern part of Hyuga-nada. The high Poisson's mantle wedge is suggesting that the zone probably corresponds to a

  16. Modeling seismic wave propagation in heterogeneous medium using overlap domain pseudospectral method

    Institute of Scientific and Technical Information of China (English)

    YAN Jiu-peng; WANG Yan-bin

    2008-01-01

    Pseudospectral method is an efficient and high accuracy numerical method for simulating seismic wave propagation in heterogeneous earth medium. Since its derivative operator is global, this method is commonly considered not suitable for parallel computation. In this paper, we introduce the parallel overlap domain decomposition scheme and give a parallel pseudospectral method implemented on distributed memory PC cluster system for modeling seismic wave propagation in heterogeneous medium. In this parallel method, the medium is decomposed into several subdomains and the wave equations are solved in each subdomain simultaneously. The solutions in each subdomain are connected through the transferring at the overlapped region. Using 2D models, we compared the parallel and traditional pseudospectral method, analyzed the accuracy of the parallel method. The results show that the parallel method can efficiently reduce computation time for the same accuracy as the traditional method. This method could be applied to large scale modeling of seismic wave propagation in 3D heterogeneous medium.

  17. Large Subduction Earthquake Simulations using Finite Source Modeling and the Offshore-Onshore Ambient Seismic Field

    Science.gov (United States)

    Viens, L.; Miyake, H.; Koketsu, K.

    2016-12-01

    Large subduction earthquakes have the potential to generate strong long-period ground motions. The ambient seismic field, also called seismic noise, contains information about the elastic response of the Earth between two seismic stations that can be retrieved using seismic interferometry. The DONET1 network, which is composed of 20 offshore stations, has been deployed atop the Nankai subduction zone, Japan, to continuously monitor the seismotectonic activity in this highly seismically active region. The surrounding onshore area is covered by hundreds of seismic stations, which are operated the National Research Institute for Earth Science and Disaster Prevention (NIED) and the Japan Meteorological Agency (JMA), with a spacing of 15-20 km. We retrieve offshore-onshore Green's functions from the ambient seismic field using the deconvolution technique and use them to simulate the long-period ground motions of moderate subduction earthquakes that occurred at shallow depth. We extend the point source method, which is appropriate for moderate events, to finite source modeling to simulate the long-period ground motions of large Mw 7 class earthquake scenarios. The source models are constructed using scaling relations between moderate and large earthquakes to discretize the fault plane of the large hypothetical events into subfaults. Offshore-onshore Green's functions are spatially interpolated over the fault plane to obtain one Green's function for each subfault. The interpolated Green's functions are finally summed up considering different rupture velocities. Results show that this technique can provide additional information about earthquake ground motions that can be used with the existing physics-based simulations to improve seismic hazard assessment.

  18. Probabilistic seismic hazard assessment of NW and central Himalayas and the adjoining region

    Indian Academy of Sciences (India)

    Madan Mohan Rout; Josodhir Das; Kamal; Ranjit Das

    2015-04-01

    The Himalayan region has undergone significant development and to ensure safe and secure progress in such a seismically vulnerable region there is a need for hazard assessment. For seismic hazard assessment, it is important to assess the quality, consistency, and homogeneity of the seismicity data collected from different sources. In the present study, an improved magnitude conversion technique has been used to convert different magnitude scales to moment magnitude scale. The study area and its adjoining region have been divided into 22 seismogenic zones based upon the geology, tectonics, and seismicity including source mechanism relevant to the region. Region specific attenuation equations have been used for seismic hazard assessment. Standard procedure for PSHA has been adopted for this study and peak ground motion is estimated for 10% and 2% probability of exceedance in 50 years at the bed rock level. For the 10% and 2% probability of exceedance in 50 years, the PGA values vary from 0.06 to 0.36 g and 0.11 to 0.65 g, respectively considering varying -value. Higher PGA values are observed in the southeast part region situated around Kaurik Fault System (KFS) and western parts of Nepal.

  19. Coupled flow and geomechanics modeling of fracture reactivation and induced seismicity in the Basel geothermal field

    Science.gov (United States)

    Tyukhova, A.; Castineira, D.; Juanes, R.

    2016-12-01

    Triggered and induced seismicity is at the cornerstone of discussions surrounding a wide range of subsurface technologies, e.g. unconventional hydrocarbon recovery, geologic carbon sequestration, underground gas storage, and geothermal energy extraction. We revisit the geothermal experiment in Basel, Switzerland, in which over 11 thousand cubic meters of water were injected into deep fractured crystalline rock. The injection took place in December 2006 and was performed at a single injection well, in three stages with increasing injection rate. Seismicity in the region increased during the experiment—with most of the seismic events occurring in the month following injection—and declined slowly after, but with seismic events still being recorded years after injection. The increase in seismicity is caused by reactivation of the pre-existing fractures: an increase in pore pressure decreases the normal effective stress across the fracture, which according to the Mohr-Coulomb failure criterion are therefore more prone to slip. The underlying processes, however, may be more complex. It is unclear the role that enhanced hydraulic connectivity in the fracture network plays on triggered seismicity, and on the emergence of seismicity clusters in space. It is also unclear what determines the delay between injection and recorded seismicity, and whether it can be explained by means of pressure propagation and/or dynamic weakening of fractures due to a drop in the friction coefficient as a result of decreased roughness from fracture slip. Here, we employ a computational model of coupled flow and geomechanics to quantitatively assess the impact of fluid injection on the recorded seismicity. We develop a simulation model that incorporates more than ten fractures, whose location, rake and dip are consistent with clusters of seismicity from a relocation of hypocenters and focal mechanisms. We adopt a multiscale description of flow (representing these fractures planes explicitly

  20. Study on the Characteristics of Seismic Activity in West China and Its neighboring Regions

    Institute of Scientific and Technical Information of China (English)

    Chen Yuwei; Shen Yelong; Ling Xueshu

    2001-01-01

    The controlling and influencing effects of the joint action of plates surrounding China on strong earthquakes in Chinese mainland are discussed, and the characteristics of seismic activities in the West of China and neighboring regions are further studied. The results show that the seismic activity in the West of China and neighboring regions not only has the characteristics of high tide and low tide alternation but also has the characteristics of rising in one region while falling in another, and the rise and fail of seismicity are in some proportion. The above characteristics are useful for the prediction of main body region of strong earthquakes in Chinese mainland, especially for the judgement of the ending time of the high fide period.

  1. Light Water Reactor Sustainability Program Advanced Seismic Soil Structure Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Bolisetti, Chandrakanth [Idaho National Lab. (INL), Idaho Falls, ID (United States); Coleman, Justin Leigh [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-06-01

    Risk calculations should focus on providing best estimate results, and associated insights, for evaluation and decision-making. Specifically, seismic probabilistic risk assessments (SPRAs) are intended to provide best estimates of the various combinations of structural and equipment failures that can lead to a seismic induced core damage event. However, in some instances the current SPRA approach has large uncertainties, and potentially masks other important events (for instance, it was not the seismic motions that caused the Fukushima core melt events, but the tsunami ingress into the facility). SPRA’s are performed by convolving the seismic hazard (this is the estimate of all likely damaging earthquakes at the site of interest) with the seismic fragility (the conditional probability of failure of a structure, system, or component given the occurrence of earthquake ground motion). In this calculation, there are three main pieces to seismic risk quantification, 1) seismic hazard and nuclear power plants (NPPs) response to the hazard, 2) fragility or capacity of structures, systems and components (SSC), and 3) systems analysis. Two areas where NLSSI effects may be important in SPRA calculations are, 1) when calculating in-structure response at the area of interest, and 2) calculation of seismic fragilities (current fragility calculations assume a lognormal distribution for probability of failure of components). Some important effects when using NLSSI in the SPRA calculation process include, 1) gapping and sliding, 2) inclined seismic waves coupled with gapping and sliding of foundations atop soil, 3) inclined seismic waves coupled with gapping and sliding of deeply embedded structures, 4) soil dilatancy, 5) soil liquefaction, 6) surface waves, 7) buoyancy, 8) concrete cracking and 9) seismic isolation The focus of the research task presented here-in is on implementation of NLSSI into the SPRA calculation process when calculating in-structure response at the area

  2. Regional passive seismic monitoring reveals dynamic glacier activity on Spitsbergen, Svalbard

    Directory of Open Access Journals (Sweden)

    Andreas Köhler

    2015-12-01

    Full Text Available Dynamic glacier activity is increasingly observed through passive seismic monitoring. We analysed near-regional-scale seismicity on the Arctic archipelago of Svalbard to identify seismic icequake signals and to study their spatial–temporal distribution within the 14-year period from 2000 until 2013. This is the first study that uses seismic data recorded on permanent broadband stations to detect and locate icequakes in different regions of Spitsbergen, the main island of the archipelago. A temporary local seismic network and direct observations of glacier calving and surging were used to identify icequake sources. We observed a high number of icequakes with clear spectral peaks between 1 and 8 Hz in different parts of Spitsbergen. Spatial clusters of icequakes could be associated with individual grounded tidewater glaciers and exhibited clear seasonal variability each year with more signals observed during the melt season. Locations at the termini of glaciers, and correlation with visual calving observations in situ at Kronebreen, a glacier in the Kongsfjorden region, show that these icequakes were caused dominantly by calving. Indirect evidence for glacier surging through increased calving seismicity was found in 2003 at Tunabreen, a glacier in central Spitsbergen. Another type of icequake was observed in the area of the Nathorstbreen glacier system. Seismic events occurred upstream of the glacier within a short time period between January and May 2009 during the initial phase of a major glacier surge. This study is the first step towards the generation and implementation of an operational seismic monitoring strategy for glacier dynamics in Svalbard.

  3. Seismic remote sensing image segmentation based on spectral histogram and dynamic region merging

    Science.gov (United States)

    Wang, Peng; Sun, Genyun; Wang, Zhenjie

    2015-12-01

    Image segmentation is the foundation of seismic information extraction from high-resolution remote sensing images. While the complexity of the seismic image brings great challenges to its segmentation. Compared with the traditional pixel-level approaches, the region-level approaches are found prevailing in dealing with the complexity. This paper addresses the seismic image segmentation problem in a region-merging style. Starting from many over-segmented regions, the image segmentation is performed by iteratively merging the neighboring regions. In the proposed algorithm, the merging criterion and merging order are two essential issues to be emphatically considered. An effective merging criterion is largely depends on the region feature and neighbor homogeneity measure. The region's spectral histogram represents the global feature of each region and enhances the discriminability of neighboring regions. Therefore, we utilize it to solve the merging criterion. Under a certain the merging criterion, a better performance could be obtained if the most similar regions are always ensured to be merged first, which can be transformed into a least-cost problem. Rather than predefine an order queue, we solve the order problem with a dynamic scheme. The proposed approach mainly contains three parts. Firstly, starting from the over-segmented regions, the spectral histograms are constructed to represent each region. Then, we use the homogeneity that combines the distance and shape measure to conduct the merge criterion. Finally, neighbor regions are dynamically merged following the dynamic program (DP) theory and breadth-first strategy. Experiments are conducted using the earthquake images, including collapsed buildings and seismic secondary geological disaster. The experimental results show that, the proposed method segments the seismic image more correctly.

  4. An observational test of the stress accumulation model based on seismicity preceding the 1992 Landers, CA earthquake

    Science.gov (United States)

    Levin, Shoshana Z.; Sammis, Charles G.; Bowman, David D.

    2006-02-01

    We test the Bowman and King [Bowman, D.D., King, G.C.P., 2001a, Accelerating seismicity and stress accumulation before large earthquakes. Geophys. Res. Lett., 28 (21), 4039-4042, Bowman, D.D., King, G.C.P., 2001b. Stress transfer and seismicity changes before large earthquakes. C. R. Acad. Sci. Paris, 333, 591-599] Stress Accumulation model by examining the evolution of seismicity rates prior to the 1992 Landers, California earthquake. The Stress Accumulation (SA) model was developed to explain observations of accelerating seismicity preceding large earthquakes. The model proposes that accelerating seismicity sequences result from the tectonic loading of large fault structures through aseismic slip in the elasto-plastic lower crust. This loading progressively increases the stress on smaller faults within a critical region around the main structure, thereby causing the observed acceleration of precursory activity. A secondary prediction of the SA model is that the precursory seismicity rates should increase first at the edges of the critical region, with the rates gradually rising over time at closer distances to the main fault. We test this prediction by examining year-long seismicity rates between 1960 and 2004, as a function of distance from the Landers rupture. To quantify the significance of trends in the seismicity rates, we auto-correlate the data, using a range of spatial and temporal lags. We find weak evidence for increased seismicity rates propagating towards the Landers rupture, but cannot conclusively distinguish these results from those obtained for a random earthquake catalog. However, we find a strong indication of periodicity in the rate fluctuations, as well as high correlation between activity 130-170 km from Landers and seismicity rates within 50 km of the Landers rupture temporally offset 1.5-2 years. The implications of this spatio-temporal correlation will be addressed in future studies.

  5. Numerical simulation analysis on Wenchuan seismic strong motion in Hanyuan region

    Science.gov (United States)

    Chen, X.; Gao, M.; Guo, J.; Li, Z.; Li, T.

    2015-12-01

    69227 deaths, 374643 injured, 17923 people missing, direct economic losses 845.1 billion, and a large number houses collapse were caused by Wenchuan Ms8 earthquake in Sichuan Province on May 12, 2008, how to reproduce characteristics of its strong ground motion and predict its intensity distribution, which have important role to mitigate disaster of similar giant earthquake in the future. Taking Yunnan-Sichuan Province, Wenchuan town, Chengdu city, Chengdu basin and its vicinity as the research area, on the basis of the available three-dimensional velocity structure model and newly topography data results from ChinaArray of Institute of Geophysics, China Earthquake Administration, 2 type complex source rupture process models with the global and local source parameters are established, we simulated the seismic wave propagation of Wenchuan Ms8 earthquake throughout the whole three-dimensional region by the GMS discrete grid finite-difference techniques with Cerjan absorbing boundary conditions, and obtained the seismic intensity distribution in this region through analyzing 50×50 stations data (simulated ground motion output station). The simulated results indicated that: (1)Simulated Wenchuan earthquake ground motion (PGA) response and the main characteristics of the response spectrum are very similar to those of the real Wenchuan earthquake records. (2)Wenchuan earthquake ground motion (PGA) and the response spectra of the Plain are much greater than that of the left Mountain area because of the low velocity of the shallow surface media and the basin effect of the Chengdu basin structure. Simultaneously, (3) the source rupture process (inversion) with far-field P-wave, GPS data and InSAR information and the Longmenshan Front Fault (source rupture process) are taken into consideration in GMS numerical simulation, significantly different waveform and frequency component of the ground motion are obtained, though the strong motion waveform is distinct asymmetric

  6. Interactive Visualizations of Complex Seismic Data and Models

    Science.gov (United States)

    Chai, C.; Ammon, C. J.; Maceira, M.; Herrmann, R. B.

    2016-12-01

    The volume and complexity of seismic data and models have increased dramatically thanks to dense seismic station deployments and advances in data modeling and processing. Seismic observations such as receiver functions and surface-wave dispersion are multidimensional: latitude, longitude, time, amplitude and latitude, longitude, period, and velocity. Three-dimensional seismic velocity models are characterized with three spatial dimensions and one additional dimension for the speed. In these circumstances, exploring the data and models and assessing the data fits is a challenge. A few professional packages are available to visualize these complex data and models. However, most of these packages rely on expensive commercial software or require a substantial time investment to master, and even when that effort is complete, communicating the results to others remains a problem. A traditional approach during the model interpretation stage is to examine data fits and model features using a large number of static displays. Publications include a few key slices or cross-sections of these high-dimensional data, but this prevents others from directly exploring the model and corresponding data fits. In this presentation, we share interactive visualization examples of complex seismic data and models that are based on open-source tools and are easy to implement. Model and data are linked in an intuitive and informative web-browser based display that can be used to explore the model and the features in the data that influence various aspects of the model. We encode the model and data into HTML files and present high-dimensional information using two approaches. The first uses a Python package to pack both data and interactive plots in a single file. The second approach uses JavaScript, CSS, and HTML to build a dynamic webpage for seismic data visualization. The tools have proven useful and led to deeper insight into 3D seismic models and the data that were used to construct them

  7. First approximations in avalanche model validations using seismic information

    Science.gov (United States)

    Roig Lafon, Pere; Suriñach, Emma; Bartelt, Perry; Pérez-Guillén, Cristina; Tapia, Mar; Sovilla, Betty

    2017-04-01

    Avalanche dynamics modelling is an essential tool for snow hazard management. Scenario based numerical modelling provides quantitative arguments for decision-making. The software tool RAMMS (WSL Institute for Snow and Avalanche Research SLF) is one such tool, often used by government authorities and geotechnical offices. As avalanche models improve, the quality of the numerical results will depend increasingly on user experience on the specification of input (e.g. release and entrainment volumes, secondary releases, snow temperature and quality). New model developments must continue to be validated using real phenomena data, for improving performance and reliability. The avalanches group form University of Barcelona (RISKNAT - UB), has studied the seismic signals generated from avalanches since 1994. Presently, the group manages the seismic installation at SLF's Vallée de la Sionne experimental site (VDLS). At VDLS the recorded seismic signals can be correlated to other avalanche measurement techniques, including both advanced remote sensing methods (radars, videogrammetry) and obstacle based sensors (pressure, capacitance, optical sender-reflector barriers). This comparison between different measurement techniques allows the group to address the question if seismic analysis can be used alone, on more additional avalanche tracks, to gain insight and validate numerical avalanche dynamics models in different terrain conditions. In this study, we aim to add the seismic data as an external record of the phenomena, able to validate RAMMS models. The seismic sensors are considerable easy and cheaper to install than other physical measuring tools, and are able to record data from the phenomena in every atmospheric conditions (e.g. bad weather, low light, freezing make photography, and other kind of sensors not usable). With seismic signals, we record the temporal evolution of the inner and denser parts of the avalanche. We are able to recognize the approximate position

  8. Quantitative description of induced seismic activity before and after the 2011 Tohoku-Oki earthquake by nonstationary ETAS models

    Science.gov (United States)

    Kumazawa, Takao; Ogata, Yosihiko

    2013-12-01

    The epidemic-type aftershock sequence (ETAS) model is extended for application to nonstationary seismic activity, including transient swarm activity or seismicity anomalies, in a seismogenic region. The time-dependent rates of both background seismicity and aftershock productivity in the ETAS model are optimally estimated from hypocenter data. These rates can provide quantitative evidence for abrupt or gradual changes in shear stress and/or fault strength due to aseismic transient causes such as triggering by remote earthquakes, slow slips, or fluid intrusions within the region. This extended model is applied to data sets from several seismic events including swarms that were induced by the M9.0 Tohoku-Oki earthquake of 2011.

  9. Analysis of Seismicity Risk Increase Triggered by Longtan Reservoir, China, Using a Fully Coupled Poroelastic Model

    Science.gov (United States)

    Deng, K.; Zhang, S.; Guo, Y.; Zhou, S.; Liu, Y.

    2015-12-01

    Impoundment of reservoirs can lead to increase in crustal pore pressure and Coulomb stress, and promotes nearby faults to fail. Abnormal seismicity increase around reservoir is often thought to be triggered by the water impounded behind the dam. In this study, we analyze the impact of Longtan reservoir in Guangxi province, southwest China, on local seismicity, which has increased significantly since the initial impoundment in October, 2006. Most of the earthquakes cluster around the reservoir according to local seismic network and CEA reports, and the greatest earthquake is of magnitude 4.2. We introduce an improved Bayesian method to show that the temporal variation of b-value is inversely correlated with the seasonal fluctuation of reservoir water level. Upon extracting background seismicity using the Epidemic Type Aftershock Sequence (ETAS) model, we show that background seismicity variation is highly related to the filling rate and volume We further investigate the mechanism of seismicity increase and reservoir impoundment by performing a fully coupled 3-D poroelastic model with the reservoir loading history as a dynamic boundary condition. An optimally oriented fault plane is chosen according to the regional stress field and GPS deformation data when calculating the induced Coulomb stress. Our results demonstrate that most earthquakes occurred within positive Coulomb stress regime, and the seismicity rate is highly related to the rate of pore pressure increase. In the next step we plan to apply the coupled poroelastic model to understand hydraulic fracturing induced earthquakes in shale gas exploration, such as the recent Fox Creek event cluster, in the western Canada sedimentary basin.

  10. Forward and inverse modelling of post-seismic deformation

    Science.gov (United States)

    Crawford, Ophelia; Al-Attar, David; Tromp, Jeroen; Mitrovica, Jerry X.

    2016-11-01

    We consider a new approach to both the forward and inverse problems in post-seismic deformation. We present a method for forward modelling post-seismic deformation in a self-gravitating, heterogeneous and compressible earth with a variety of linear and non-linear rheologies. We further demonstrate how the adjoint method can be applied to the inverse problem both to invert for rheological structure and to calculate the sensitivity of a given surface measurement to changes in rheology or time-dependence of the source. Both the forward and inverse aspects are illustrated with several numerical examples implemented in a spherically symmetric earth model.

  11. Forward and inverse modelling of post-seismic deformation

    Science.gov (United States)

    Crawford, Ophelia; Al-Attar, David; Tromp, Jeroen; Mitrovica, Jerry X.

    2017-02-01

    We consider a new approach to both the forward and inverse problems in post-seismic deformation. We present a method for forward modelling post-seismic deformation in a self-gravitating, heterogeneous and compressible earth with a variety of linear and nonlinear rheologies. We further demonstrate how the adjoint method can be applied to the inverse problem both to invert for rheological structure and to calculate the sensitivity of a given surface measurement to changes in rheology or time-dependence of the source. Both the forward and inverse aspects are illustrated with several numerical examples implemented in a spherically symmetric earth model.

  12. Seismic Site Survey for New Regional Seismic Array Station in Morocco

    Science.gov (United States)

    2005-08-22

    Moroccan seismic array followed this process. I Morocco Noise Survey Report Pre-Survey Studies The initial step in selecting candidate sites was to gather...32’W 5ŗU’W rn 4 Figre13 Hghresluio tporapicma o sme re, it crcl a te ppoxiat lcaioof~~~~ th0rooe ary Mooco oseSuve eprt1 5൰’W 5•35’W 5൦’W ,d...cooperative from the main Moroccan power grid, and that the power was reliable. 21 Morocco Noise Survey Report Land Owner. The land is state-owned. i’ý5oIW 5 45

  13. New inferences from spectral seismic energy measurement of a link between regional seismicity and volcanic activity at Mt. Etna, Italy

    Science.gov (United States)

    Ortiz, R.; Falsaperla, S.; Marrero, J. M.; Messina, A.

    2009-04-01

    The existence of a relationship between regional seismicity and changes in volcanic activity has been the subject of several studies in the last years. Generally, activity in basaltic volcanoes such as Villarica (Chile) and Tungurahua (Ecuador) shows very little changes after the occurrence of regional earthquakes. In a few cases volcanic activity has changed before the occurrence of regional earthquakes, such as observed at Teide, Tenerife, in 2004 and 2005 (Tárraga et al., 2006). In this paper we explore the possible link between regional seismicity and changes in volcanic activity at Mt. Etna in 2006 and 2007. On 24 November, 2006 at 4:37:40 GMT an earthquake of magnitude 4.7 stroke the eastern coast of Sicily. The epicenter was localized 50 km SE of the south coast of the island, and at about 160 km from the summit craters of Mt. Etna. The SSEM (Spectral Seismic Energy Measurement) of the seismic signal at stations at 1 km and 6 km from the craters highlights that four hours before this earthquake the energy associated with volcanic tremor increased, reached a maximum, and finally became steady when the earthquake occurred. Conversely, neither before nor after the earthquake, the SSEM of stations located between 80 km and 120 km from the epicentre and outside the volcano edifice showed changes. On 5 September, 2007 at 21:24:13 GMT an earthquake of magnitude 3.2 and 7.9 km depth stroke the Lipari Island, at the north of Sicily. About 38 hours before the earthquake occurrence, there was an episode of lava fountain lasting 20 hours at Etna volcano. The SSEM of the seismic signal recorded during the lava fountain at a station located at 6 km from the craters highlights changes heralding this earthquake ten hours before its occurrence using the FFM method (e.g., Voight, 1988; Ortiz et al., 2003). A change in volcanic activity - with the onset of ash emission and Strombolian explosions - was observed a couple of hours before the occurrence of the regional

  14. Detection of hydrogeochemical seismic precursors by a statistical learning model

    Directory of Open Access Journals (Sweden)

    L. Castellana

    2008-11-01

    Full Text Available The problem of detecting the occurrence of an earthquake precursor is faced in the general framework of the statistical learning theory. The aim of this work is both to build models able to detect seismic precursors from time series of different geochemical signals and to provide an estimate of number of false positives. The model we used is k-Nearest-Neighbor classifier for discriminating "no-disturbed signal", "seismic precursor" and "co-post seismic precursor" in time series relative to thirteen different hydrogeochemical parameters collected in water samples from a natural spring in Kamchachta (Russia peninsula. The measurements collected are ion content (Na, Cl, Ca, HCO3, H3BO3, parameters (pH, Q, T and gases (N2, CO2, CH4, O2, Ag. The classification error is measured by Leave-K-Out-Cross-Validation procedure. Our study shows that the most discriminative ions for detecting seismic precursors are Cl and Na having an error rates of 15%. Moreover, the most discriminative parameters and gases are Q and CH4 respectively, with error rate of 21%. The ions result the most informative hydrogeochemicals for detecting seismic precursors due to the peculiarities of the mechanisms involved in earthquake preparation. Finally we show that the information collected some month before the event under analysis are necessary to improve the classification accuracy.

  15. Support Vector Machine Model for Automatic Detection and Classification of Seismic Events

    Science.gov (United States)

    Barros, Vesna; Barros, Lucas

    2016-04-01

    The automated processing of multiple seismic signals to detect, localize and classify seismic events is a central tool in both natural hazards monitoring and nuclear treaty verification. However, false detections and missed detections caused by station noise and incorrect classification of arrivals are still an issue and the events are often unclassified or poorly classified. Thus, machine learning techniques can be used in automatic processing for classifying the huge database of seismic recordings and provide more confidence in the final output. Applied in the context of the International Monitoring System (IMS) - a global sensor network developed for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) - we propose a fully automatic method for seismic event detection and classification based on a supervised pattern recognition technique called the Support Vector Machine (SVM). According to Kortström et al., 2015, the advantages of using SVM are handleability of large number of features and effectiveness in high dimensional spaces. Our objective is to detect seismic events from one IMS seismic station located in an area of high seismicity and mining activity and classify them as earthquakes or quarry blasts. It is expected to create a flexible and easily adjustable SVM method that can be applied in different regions and datasets. Taken a step further, accurate results for seismic stations could lead to a modification of the model and its parameters to make it applicable to other waveform technologies used to monitor nuclear explosions such as infrasound and hydroacoustic waveforms. As an authorized user, we have direct access to all IMS data and bulletins through a secure signatory account. A set of significant seismic waveforms containing different types of events (e.g. earthquake, quarry blasts) and noise is being analysed to train the model and learn the typical pattern of the signal from these events. Moreover, comparing the performance of the support

  16. Seismic Halos Around Active Regions: An MHD Theory

    CERN Document Server

    Hanasoge, Shravan M

    2007-01-01

    Comprehending the manner in which magnetic fields affect propagating waves is a first step toward the helioseismic construction of accurate models of active region sub-surface structure and dynamics. Here, we present a numerical method to compute the linear interaction of waves with magnetic fields embedded in a solar-like stratified background. The ideal Magneto-Hydrodynamic (MHD) equations are solved in a 3-dimensional box that straddles the solar photosphere, extending from 35 Mm within to 1.2 Mm into the atmosphere. One of the challenges in performing these simulations involves generating a Magneto-Hydro-Static (MHS) state wherein the stratification assumes horizontal inhomogeneity in addition to the strong vertical stratification associated with the near-surface layers. Keeping in mind that the aim of this effort is to understand and characterize linear MHD interactions, we discuss a means of computing statically consistent background states. Results from a simulation of waves interacting with a flux tub...

  17. Seismic anisotropy of the lithosphere/asthenosphere system beneath the Rwenzori region of the Albertine Rift

    Science.gov (United States)

    Homuth, B.; Löbl, U.; Batte, A. G.; Link, K.; Kasereka, C. M.; Rümpker, G.

    2016-09-01

    Shear-wave splitting measurements from local and teleseismic earthquakes are used to investigate the seismic anisotropy in the upper mantle beneath the Rwenzori region of the East African Rift system. At most stations, shear-wave splitting parameters obtained from individual earthquakes exhibit only minor variations with backazimuth. We therefore employ a joint inversion of SKS waveforms to derive hypothetical one-layer parameters. The corresponding fast polarizations are generally rift parallel and the average delay time is about 1 s. Shear phases from local events within the crust are characterized by an average delay time of 0.04 s. Delay times from local mantle earthquakes are in the range of 0.2 s. This observation suggests that the dominant source region for seismic anisotropy beneath the rift is located within the mantle. We use finite-frequency waveform modeling to test different models of anisotropy within the lithosphere/asthenosphere system of the rift. The results show that the rift-parallel fast polarizations are consistent with horizontal transverse isotropy (HTI anisotropy) caused by rift-parallel magmatic intrusions or lenses located within the lithospheric mantle—as it would be expected during the early stages of continental rifting. Furthermore, the short-scale spatial variations in the fast polarizations observed in the southern part of the study area can be explained by effects due to sedimentary basins of low isotropic velocity in combination with a shift in the orientation of anisotropic fabrics in the upper mantle. A uniform anisotropic layer in relation to large-scale asthenospheric mantle flow is less consistent with the observed splitting parameters.

  18. Seismicity and coupled deformation modeling at the Coso Geothermal Field

    Science.gov (United States)

    Kaven, J. O.; Hickman, S. H.; Davatzes, N. C.

    2015-12-01

    Micro-seismicity in geothermal reservoirs, in particular in enhanced geothermal systems (EGS), is a beneficial byproduct of injection and production, as it can indicate the generation of high-permeability pathways on either pre-existing or newly generated faults and fractures. The hazard of inducing an earthquake large enough to be felt at the surface, however, is not easily avoided and has led to termination of some EGS projects. To explore the physical processes leading to permeability creation and maintenance in geothermal systems and the physics of induced earthquakes , we investigated the evolution of seismicity and the factors controlling the migration, moment release rate, and timing of seismicity in the Coso Geothermal Field (CGF). We report on seismicity in the CGF that has been relocated with high precision double-difference relocation techniques and simultaneous velocity inversions to understand hydrologic reservoir compartmentalization and the nature of subsurface boundaries to fluid flow. We find that two distinct compartments are present within the CGF, which are divided by an aseismic gap showing a relatively low Vp/Vs ratio, likely indicating lower temperatures or lower pore pressures within the gap than in the adjacent reservoir compartments. Well-located events with Mw> 3.5 tend to map onto reactivated fault structures that were revealed when imaged by the relocated micro-seismicity. We relate the temporal and spatial migration of moment release rate to the injection and production histories in the reservoir by employing a thermo-poro-elastic finite element model that takes into account the compartment boundaries defined by the seismicity. We find that pore pressure effects alone are not responsible for the migration of seismicity and that poro-elastic and thermo-elastic stress changes are needed in addition to fluid pressure effects to account for the observed moment release rates.

  19. The Impact of the Subduction Modeling Beneath Calabria on Seismic Hazard

    Science.gov (United States)

    Morasca, P.; Johnson, W. J.; Del Giudice, T.; Poggi, P.; Traverso, C.; Parker, E. J.

    2014-12-01

    The aim of this work is to better understand the influence of subduction beneath Calabria on seismic hazard, as very little is known about present-day kinematics and the seismogenic potential of the slab interface in the Calabrian Arc region. This evaluation is significant because, depending on stress conditions, subduction zones can vary from being fully coupled to almost entirely decoupled with important consequences in the seismic hazard assessment. Although the debate is still open about the current kinematics of the plates and microplates lying in the region and the degree of coupling of Ionian lithosphere beneath Calabria, GPS data suggest that this subduction is locked in its interface sector. Also the lack of instrumentally recorded thrust earthquakes suggests this zone is locked. The current seismotectonic model developed for the Italian National territory is simplified in this area and does not reflect the possibility of locked subduction beneath the Calabria that could produce infrequent, but very large earthquakes associated with the subduction interface. Because of this we have conducted an independent seismic source analysis to take into account the influence of subduction as part of a regional seismic hazard analysis. Our final model includes two separate provinces for the subduction beneath the Calabria: inslab and interface. From a geometrical point of view the interface province is modeled with a depth between 20-50 km and a dip of 20°, while the inslab one dips 70° between 50 -100 km. Following recent interpretations we take into account that the interface subduction is possibly locked and, in such a case, large events could occur as characteristic earthquakes. The results of the PSHA analysis show that the subduction beneath the Calabrian region has an influence in the total hazard for this region, especially for long return periods. Regional seismotectonic models for this region should account for subduction.

  20. Seismic features of the June 1999 tectonic swarm in the Stromboli volcano region, Italy

    Science.gov (United States)

    Falsaperla, S.; Alparone, S.; Spampinato, S.

    2003-07-01

    Crustal tectonic seismicity in the Southern Tyrrhenian Sea is characterized by the high occurrence rates of earthquakes to the west of the alignment of Salina, Lipari and Vulcano islands in the Aeolian archipelago. Only a few earthquakes affect the crustal region east of these islands, whereas intermediate and deep seismicity plays a relevant role. Based on this evidence, two aspects of the seismic swarm recorded at the Aeolian Island Seismic Network between June 6 and 17, 1999 looked anomalous. The first aspect concerned the number of earthquakes (78) that affected the Stromboli submarine edifice in a short time interval. Secondly, despite the low maximum magnitude Md 3.2 reached, the cumulative strain release was conspicuous in comparison with previous swarms in this region. We localized the swarm about 6 km northeast of Stromboli, at a depth between 8 and 12 km. The source region was identified using standard methods of hypocentral location, as well as azimuth analysis. It is worth noting that the volcanic activity at Stromboli did not change significantly during the swarm nor throughout the following months. Therefore, the seismic swarm had no link with volcanic activity observed at the surface. Most of the earthquakes shared similar waveform and frequency content, and can be divided into families. We identified some earthquakes - with magnitude up to Md 3 - having relatively low frequency content at different seismic stations. This anomalous feature leads us to hypothesize the presence of fluid circulation and/or propagation of seismic waves in a ductile medium. Our hypothesis is in agreement with studies on marine geology, which highlight various forms of submarine volcanism in the southern basin of the Tyrrhenian Sea.

  1. A probabilistic seismic hazard assessment for Greece and the surrounding region including site-specific considerations

    Directory of Open Access Journals (Sweden)

    P. Mäntyniemi

    2004-06-01

    Full Text Available A probabilistic approach was applied to map the seismic hazard in Greece and the surrounding region. The procedure does not require any specification of seismic sources or/and seismic zones and allows for the use of the whole seismological record, comprising both historical and instrumental data, available for the region of interest. The new seismic hazard map prepared for Greece and its vicinity specifies a 10% probability of exceedance of the given Peak Ground Acceleration (PGA values for shallow seismicity and intermediate soil conditions for an exposure time of 50 years. When preparing the map, the new PGA attenuation relation given by Margaris et al. (2001 was employed. The new map shows a spatial distribution of the seismic hazard that corresponds well with the features of shallow seismicity within the examined region. It depicts the level of seismic hazard in which the exceedance of the PGA value of 0.25 g may be expected to occur within limited areas. The highest estimated levels of seismic hazard inside the territory of Greece are found in the Northern Sporades Islands, where PGA values in excess of 0.50 g are reached at individual sites, and in the Zante Island in Western Greece, where PGA values in the range of 0.35 g to 0.40 g are obtained at more numerous localities. High values are also observed in the sea between the Karpathos and Rhodes islands, near the Island of Amorgos (Cyclades Archipelago and in the Southwestern Peloponnesus. The levels of seismic hazard at the sites of seven Greek cities (Athens, Jannena, Kalamata, Kozani, Larisa, Rhodes and Thessaloniki were also estimated in terms of probabilities that a given PGA value will be exceeded at least once during a time interval of 1, 50 and 100 years at those sites. These probabilities were based on the maximum horizontal PGA values obtained by applying the design earthquake procedure, and the respective median values obtained were 0.24 g for Athens, 0.28 g

  2. Determining resolvability of mantle plumes with synthetic seismic modeling

    Science.gov (United States)

    Maguire, R.; Van Keken, P. E.; Ritsema, J.; Fichtner, A.; Goes, S. D. B.

    2014-12-01

    Hotspot volcanism in locations such as Hawaii and Iceland is commonly thought to be associated with plumes rising from the deep mantle. In theory these dynamic upwellings should be visible in seismic data due to their reduced seismic velocity and their effect on mantle transition zone thickness. Numerous studies have attempted to image plumes [1,2,3], but their deep mantle origin remains unclear. In addition, a debate continues as to whether lower mantle plumes are visible in the form of body wave travel time delays, or whether such delays will be erased due to wavefront healing. Here we combine geodynamic modeling of mantle plumes with synthetic seismic waveform modeling in order to quantitatively determine under what conditions mantle plumes should be seismically visible. We model compressible plumes with phase changes at 410 km and 670 km, and a viscosity reduction in the upper mantle. These plumes thin from greater than 600 km in diameter in the lower mantle, to 200 - 400 km in the upper mantle. Plume excess potential temperature is 375 K, which maps to seismic velocity reductions of 4 - 12 % in the upper mantle, and 2 - 4 % in the lower mantle. Previous work that was limited to an axisymmetric spherical geometry suggested that these plumes would not be visible in the lower mantle [4]. Here we extend this approach to full 3D spherical wave propagation modeling. Initial results using a simplified cylindrical plume conduit suggest that mantle plumes with a diameter of 1000 km or greater will retain a deep mantle seismic signature. References[1] Wolfe, Cecily J., et al. "Seismic structure of the Iceland mantle plume." Nature 385.6613 (1997): 245-247. [2] Montelli, Raffaella, et al. "Finite-frequency tomography reveals a variety of plumes in the mantle." Science 303.5656 (2004): 338-343. [3] Schmandt, Brandon, et al. "Hot mantle upwelling across the 660 beneath Yellowstone." Earth and Planetary Science Letters 331 (2012): 224-236. [4] Hwang, Yong Keun, et al

  3. Seismicity and fluid injections: numerical modelling of fault activation

    Science.gov (United States)

    Murphy, S.; O'Brien, G.; Bean, C.; McCloskey, J.; Nalbant, S.

    2012-04-01

    Injection of fluid into the subsurface is a common technique and is used to optimise returns from hydrocarbon plays (e.g. enhanced oil recovery, hydrofacturing of shales) and geothermal sites as well as for the sequestering carbon dioxide. While it is well understood that stress perturbations caused by fluid injections can induce/trigger earthquakes; the modelling of such hazard is still in its infancy. By combining fluid flow and seismicity simulations we have created a numerical model for investigating induced seismicity over large time periods so that we might examine the role of operational and geological factors in seismogenesis around a sub-surface fluid injection. In our model, fluid injection is simulated using pore fluid movement throughout a permeable layer from a high-pressure point source using a lattice Boltzmann scheme. We can accommodate complicated geological structures in our simulations. Seismicity is modelled using a quasi-dynamic relationship between stress and slip coupled with a rate-and state friction law. By spatially varying the frictional parameters, the model can reproduce both seismic and aseismic slip. Static stress perturbations (due to either to fault cells slipping or fluid injection) are calculated using analytical solutions for slip dislocations/pressure changes in an elastic half space. An adaptive time step is used in order to increase computational efficiency and thus allow us to model hundreds of years of seismicity. As a case study, we investigate the role that relative fault - injection location plays in seismic activity. To do this we created three synthetic catalogues with only the relative location of the fault from the point of injection varying between the models. In our control model there is no injection meaning it contains only tectonically triggered events. In the other two catalogues, the injection site is placed below and adjacent to the fault respectively. The injection itself is into a permeable thin planar layer

  4. Source characteristics of the seismic sequences in the Eastern Carpathians foredeep region (Romania)

    Science.gov (United States)

    Popescu, Emilia; Radulian, Mircea

    2001-08-01

    The source parameters and scaling properties for two seismic areas (Vrâncioaia and Râmnicu Sărat) of the Carpathians Mountains foredeep, adjacent to the Vrancea seismic region, are analyzed by standard time and frequency domain methods and empirical Green's function deconvolution. The study area is characterized by distinct shallow seismicity clusters with small and moderate-size earthquakes ( Mreology. Our paper shows the efficiency of the empirical Green's function deconvolution in eliminating the instrument, path and site effects for the earthquake sequences in the Râmnicu Sărat region. The apparent source time function is generally well constrained, as demonstrated by our tests using in parallel both, appropriate Green's functions of different sizes, and instruments with different frequency bandwidth.

  5. Modelling of Seismic Ground Motion in Santiago de Cuba City from Earthquakes in Oriente Fault Seismic Zone

    Science.gov (United States)

    Alvarez, L.; Panza, G. F.; Vaccari, F.; González, B. E.

    We present the results of complete P-SV and SH waves modelling, up to a maximum frequency of 1Hz, along two profiles in Santiago de Cuba city. The seismic sources are located in the depth range from 10 to 40km on the Oriente fault zone at distances of several tens of kilometres from the city. The calculation has been made by a hybrid method: Modal summation in the regional anelastic model (one-dimensional) where the source is buried, and finite differences in the local sedimentary anelastic models (two-dimensional). The analysis of the influence of the depth and of the distance of the source on the site effects shows that standard traditional methods, based on the deconvolution analysis of the rock outcrop motion, can lead to erroneous results.

  6. Friction at seismic slip rates: testing thermal weakening models experimentally

    Science.gov (United States)

    Nielsen, S. B.; Spagnuolo, E.; Violay, M.; Di Toro, G.

    2013-12-01

    Recent experiments systematically explore rock friction under crustal earthquake conditions (fast slip rate 1desing an efficient and accurate wavenumber approximation for a solution of the temperature evolution on the fault. Finally, we propose a compact and paractical model based on a small number of memory variables for the implementation of thermal weakening friction in seismic fault simulations.

  7. Modelling seismic waves around underground openings in fractured rock

    CSIR Research Space (South Africa)

    Hildyard, MW

    2002-01-03

    Full Text Available The potential for large excavation-induced seismic events may be recognised, even if the timing of an event may be inherently unpredictable. In this case, modelling the wave propagation from a potential event could allow the dynamic motions around...

  8. Modeling of seismic data in the downward continuation approach

    NARCIS (Netherlands)

    Stolk, Christiaan C.; Hoop, de Maarten V.

    2005-01-01

    Seismic data are commonly modeled by a high-frequency single scattering approximation. This amounts to a linearization in the medium coefficient about a smooth background. The discontinuities are contained in the medium perturbation. The high-frequency part of the wavefield in the background medium

  9. Characteristics of regional seismic waves from the 2006 and 2009 North Korean nuclear explosion tests

    Science.gov (United States)

    Rhee, S.; Hong, T.

    2009-12-01

    Two North Korean nuclear explosion (UNE) tests were conducted in 2006 and 2009. The events are the first UNEs in the 21st century. The UNEs were well recorded by dense regional seismic networks in Korea, Japan and China. The UNEs provide unique regional seismic waveforms with high signal-to-noise ratios. However, the continental crust in the Korean Peninsula changes abruptly into a transitional structure between continental and oceanic crusts across the eastern shore. The complex geological and tectonic structures around the Korean Peninsula cause significant variations in regional waveforms. One outstanding question is whether typical seismic features are still observed in the North Korean UNE records. Another question is whether conventional discrimination techniques can be applicable for the North Korean UNEs. P/S amplitude ratios are widely applied for seismic discrimination. In this study, we describe the features of regional waveforms of the North Korean UNEs. We investigate the composition of regional shear energy by analyzing three-component seismograms for various frequency bands. The shear-energy contents are compared with those of comparable natural earthquakes. We find that Pn/Lg amplitude ratios are 3-4 times larger than those of earthquakes. The UNEs records show that the Pn/Lg amplitude ratios on the vertical components are lower than those on the horizontal components in the frequencies around 1 Hz.

  10. Seismic behavior of tire waste-sand mixtures for transportation infrastructure in cold regions

    Institute of Scientific and Technical Information of China (English)

    Aye Edinliler; Ozgur Yildiz

    2015-01-01

    Tire wastes have many properties that are valuable from a geotechnical engineering perspective, such as low density, high strength, thermal insulation, energy absorption capacity, permeability, durability, compressibility, resilience, and high frictional strength. Thus, tire wastes offer good thermal characteristics in resisting frost penetration and have good drainage characteristics, being as permeable as coarse granular soil for fill materials. The many advantages of tire wastes make the material suitable for transportation infrastructure construction in cold regions. Also, tire wastes with high damping prop-erty make them a preferable admixture with sand for transportation infrastructures in seismic regions. This study aimed to determine the seismic performance of certain tire waste-sand mixtures in cold regions. A 70% sand-30% tire crumb mixture by weight (TC30) with a very high damping property was selected for analysis as an engineering material for transportation infrastructure. Small-scale shake-table tests were conducted on this material as well as on a sand-only sample under two different temperatures, 0 °C and 20 °C, to simulate cold-region and moderate-temperature performance, respectively. The 1999İzmit Earthquake Excitation (EW) (Mw=7.4) was taken as the input motion. Test results showed that the tire waste-sand mixture at 0 °C showed better seismic performance than that at room temperature, suggesting that a tire waste-sand mixture in cold regions may reduce seismic hazards to infrastructure.

  11. Automatic detection of alpine rockslides in continuous seismic data using hidden Markov models

    Science.gov (United States)

    Dammeier, Franziska; Moore, Jeffrey R.; Hammer, Conny; Haslinger, Florian; Loew, Simon

    2016-02-01

    Data from continuously recording permanent seismic networks can contain information about rockslide occurrence and timing complementary to eyewitness observations and thus aid in construction of robust event catalogs. However, detecting infrequent rockslide signals within large volumes of continuous seismic waveform data remains challenging and often requires demanding manual intervention. We adapted an automatic classification method using hidden Markov models to detect rockslide signals in seismic data from two stations in central Switzerland. We first processed 21 known rockslides, with event volumes spanning 3 orders of magnitude and station event distances varying by 1 order of magnitude, which resulted in 13 and 19 successfully classified events at the two stations. Retraining the models to incorporate seismic noise from the day of the event improved the respective results to 16 and 19 successful classifications. The missed events generally had low signal-to-noise ratio and small to medium volumes. We then processed nearly 14 years of continuous seismic data from the same two stations to detect previously unknown events. After postprocessing, we classified 30 new events as rockslides, of which we could verify three through independent observation. In particular, the largest new event, with estimated volume of 500,000 m3, was not generally known within the Swiss landslide community, highlighting the importance of regional seismic data analysis even in densely populated mountainous regions. Our method can be easily implemented as part of existing earthquake monitoring systems, and with an average event detection rate of about two per month, manual verification would not significantly increase operational workload.

  12. Upper Mantle Structure beneath the Chinese Capital Region from Teleseismic Finite-Frequency Seismic Tomography

    Science.gov (United States)

    Yang, F.; Huang, J.

    2009-12-01

    In this study, we applied the finite-frequency seismic tomography(FFST) to teleseismic waveform data to determine 3-D P-wave velocity structure of the upper mantle under the Chinese capital region. The seismic waveform data from more than 300 teleseismic events recorded by the Chinese digital Capital Seismic Network during the period from September 2003 to December 2005 was used in this study. We obtained 18499 high accuracy P-wave relative travel-times by filtering these waveform data on the vertical component into high-, intermediate-, low-frequency bands (1.0-2.0, 0.1-1.0 and 0.05-0.1 hz, respectively) and the multi-channel waveform cross correlation measurement. The 3-D Fréchet sensitivity kernels were calculated by paraxial approximation for each frequency band. We established observation equations with these measured relative travel-times and 3-D Fréchet sensitivity kernels and then determined the 3-D velocity structure by inverting the observation equations. Our results show there are distinct differences of deep velocity structure down to 150 km depth under the four tectonic units of present study region. The Yanshan uplift exhibited the high velocity(high-V) feature. Under the Taihangshan uplift, broad low velocity(low-V) are visible, but it also shows up as small high-V anomalies. A large scale prominent low-V anomaly was revealed in the shallow upper mantle under the North China basin and Bohai bay. In the North China basin the low-V anomaly generally extend from 50 km to 150 km depth, but in the Bohai bay, this low-V anomaly gradually extend down to 200 km depth. The depth of this low-V anomaly is 50-70 km under the North China basin and Bohai bay, which is consistent with the depth of high conductivity layer in the upper mantle determined by the measurement of magnetotelluric sounding and heat flow. This result shows lithosphere thinning in the North China basin and Bohai bay. Most of large earthquakes occurred in the Zhangjiakou-Penglai fault zone

  13. Seismic Hazard and risk assessment for Romania -Bulgaria cross-border region

    Science.gov (United States)

    Simeonova, Stela; Solakov, Dimcho; Alexandrova, Irena; Vaseva, Elena; Trifonova, Petya; Raykova, Plamena

    2016-04-01

    Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their social and economical impact on the urban environment. Global seismic hazard and vulnerability to earthquakes are steadily increasing as urbanization and development occupy more areas that are prone to effects of strong earthquakes. The assessment of the seismic hazard and risk is particularly important, because it provides valuable information for seismic safety and disaster mitigation, and it supports decision making for the benefit of society. Romania and Bulgaria, situated in the Balkan Region as a part of the Alpine-Himalayan seismic belt, are characterized by high seismicity, and are exposed to a high seismic risk. Over the centuries, both countries have experienced strong earthquakes. The cross-border region encompassing the northern Bulgaria and southern Romania is a territory prone to effects of strong earthquakes. The area is significantly affected by earthquakes occurred in both countries, on the one hand the events generated by the Vrancea intermediate-depth seismic source in Romania, and on the other hand by the crustal seismicity originated in the seismic sources: Shabla (SHB), Dulovo, Gorna Orjahovitza (GO) in Bulgaria. The Vrancea seismogenic zone of Romania is a very peculiar seismic source, often described as unique in the world, and it represents a major concern for most of the northern part of Bulgaria as well. In the present study the seismic hazard for Romania-Bulgaria cross-border region on the basis of integrated basic geo-datasets is assessed. The hazard results are obtained by applying two alternative approaches - probabilistic and deterministic. The MSK64 intensity (MSK64 scale is practically equal to the new EMS98) is used as output parameter for the hazard maps. We prefer to use here the macroseismic intensity instead of PGA, because it is directly related to the degree of damages and, moreover, the epicentral intensity is the original

  14. Seismic hazard assessment of Sub-Saharan Africa using geodetic strain rate models

    Science.gov (United States)

    Poggi, Valerio; Pagani, Marco; Weatherill, Graeme; Garcia, Julio; Durrheim, Raymond J.; Mavonga Tuluka, Georges

    2016-04-01

    The East African Rift System (EARS) is the major active tectonic feature of the Sub-Saharan Africa (SSA) region. Although the seismicity level of such a divergent plate boundary can be described as moderate, several earthquakes have been reported in historical times causing a non-negligible level of damage, albeit mostly due to the high vulnerability of the local buildings and structures. Formulation and enforcement of national seismic codes is therefore an essential future risk mitigation strategy. Nonetheless, a reliable risk assessment cannot be done without the calibration of an updated seismic hazard model for the region. Unfortunately, the major issue in assessing seismic hazard in Sub-Saharan Africa is the lack of basic information needed to construct source and ground motion models. The historical earthquake record is largely incomplete, while instrumental catalogue is complete down to sufficient magnitude only for a relatively short time span. In addition, mapping of seimogenically active faults is still an on-going program. Recent studies have identified major seismogenic lineaments, but there is substantial lack of kinematic information for intermediate-to-small scale tectonic features, information that is essential for the proper calibration of earthquake recurrence models. To compensate this lack of information, we experiment the use of a strain rate model recently developed by Stamps et al. (2015) in the framework of a earthquake hazard and risk project along the EARS supported by USAID and jointly carried out by GEM and AfricaArray. We use the inferred geodetic strain rates to derive estimates of total scalar moment release, subsequently used to constrain earthquake recurrence relationships for both area (as distributed seismicity) and fault source models. The rates obtained indirectly from strain rates and more classically derived from the available seismic catalogues are then compared and combined into a unique mixed earthquake recurrence model

  15. Seismic source inversion using Green's reciprocity and a 3-D structural model for the Japanese Islands

    Science.gov (United States)

    Simutė, S.; Fichtner, A.

    2015-12-01

    We present a feasibility study for seismic source inversions using a 3-D velocity model for the Japanese Islands. The approach involves numerically calculating 3-D Green's tensors, which is made efficient by exploiting Green's reciprocity. The rationale for 3-D seismic source inversion has several aspects. For structurally complex regions, such as the Japan area, it is necessary to account for 3-D Earth heterogeneities to prevent unknown structure polluting source solutions. In addition, earthquake source characterisation can serve as a means to delineate existing faults. Source parameters obtained for more realistic Earth models can then facilitate improvements in seismic tomography and early warning systems, which are particularly important for seismically active areas, such as Japan. We have created a database of numerically computed 3-D Green's reciprocals for a 40°× 40°× 600 km size area around the Japanese Archipelago for >150 broadband stations. For this we used a regional 3-D velocity model, recently obtained from full waveform inversion. The model includes attenuation and radial anisotropy and explains seismic waveform data for periods between 10 - 80 s generally well. The aim is to perform source inversions using the database of 3-D Green's tensors. As preliminary steps, we present initial concepts to address issues that are at the basis of our approach. We first investigate to which extent Green's reciprocity works in a discrete domain. Considering substantial amounts of computed Green's tensors we address storage requirements and file formatting. We discuss the importance of the initial source model, as an intelligent choice can substantially reduce the search volume. Possibilities to perform a Bayesian inversion and ways to move to finite source inversion are also explored.

  16. Analysis of the seismicity in the region of Mirovo salt mine after 8 years monitoring

    Science.gov (United States)

    Dimitrova, Liliya; Solakov, Dimcho; Simeonova, Stela; Aleksandrova, Irena; Georgieva, Gergana

    2015-04-01

    Mirovo salt deposit is situated in the NE part of Bulgaria and 5 kilometers away from the town of Provadiya. The mine is in operation since 1956. The salt is produced by dilution and extraction of the brine to the surface. A system of chambers-pillars is formed within the salt body as a result of the applied technology. The mine is situated in a seismically quiet part of the state. The region is characterized with complex geological structure and several faults. During the last 3 decades a large number of small and moderate earthquakes (MVPN and MAN networks of the Bulgarian Telecommunication Company. Common processing and interpretation of the data from LSN and the national seismic network is performed. Real-time and interactive data processing are performed by the Seismic Network Data Processor (SNDP) software package. More than 700 earthquakes are registered by the LSN within 30km region around the mine during the 8 years monitoring. First we processed the data and compile a catalogue of the earthquakes occur within the studied region (30km around the salt mine). Spatial pattern of seismicity is analyzed. A large number of the seismic events occurred within the northern and north-western part of the salt body. Several earthquakes occurred in close vicinity of the mine. Concerning that the earthquakes could be tectonic and/or induced an attempt is made to find criteria to distinguish natural from induced seismicity. To characterize and distinguish the main processes active in the area we also made waveform and spectral analysis of a number of earthquakes.

  17. Regional seismic hazard for Revithoussa, Greece: an earthquake early warning Shield and selection of alert signals

    Directory of Open Access Journals (Sweden)

    Y. Xu

    2003-01-01

    Full Text Available The feasibility of an earthquake early warning Shield in Greece is being explored as a European demonstration project. This will be the first early warning system in Europe. The island of Revithoussa is a liquid natural gas storage facility near Athens from which a pipeline runs to a gas distribution centre in Athens. The Shield is being centred on these facilities. The purpose here is to analyze seismicity and seismic hazard in relation to the Shield centre and the remote sensor sites in the Shield network, eventually to help characterize the hazard levels, seismic signals and ground vibration levels that might be observed or create an alert situation at a station. Thus this paper mainly gives estimation of local seismic hazard in the regional working area of Revithoussa by studying extreme peak ground acceleration (PGA and magnitudes. Within the Shield region, the most important zone to be detected is WNW from the Shield centre and is at a relatively short distance (50 km or less, the Gulf of Corinth (active normal faults region. This is the critical zone for early warning of strong ground shaking. A second key region of seismicity is at an intermediate distance (100 km or more from the centre, the Hellenic seismic zone south or southeast from Peloponnisos. A third region to be detected would be the northeastern region from the centre and is at a relatively long distance (about 150 km, Lemnos Island and neighboring region. Several parameters are estimated to characterize the seismicity and hazard. These include: the 50-year PGA with 90% probability of not being exceeded (pnbe using Theodulidis & Papazachos strong motion attenuation for Greece, PGANTP; the 50-year magnitude and also at the 90% pnbe, M50 and MP50, respectively. There are also estimates of the earthquake that is most likely to be felt at a damaging intensity level, these are the most perceptible earthquakes at intensities VI, VII and VIII with magnitudes MVI, MVII and MVIII

  18. Post-seismic relaxation theory on laterally heterogeneous viscoelastic model

    Science.gov (United States)

    Pollitz, F.F.

    2003-01-01

    Investigation was carried out into the problem of relaxation of a laterally heterogeneous viscoelastic Earth following an impulsive moment release event. The formal solution utilizes a semi-analytic solution for post-seismic deformation on a laterally homogeneous Earth constructed from viscoelastic normal modes, followed by application of mode coupling theory to derive the response on the aspherical Earth. The solution is constructed in the Laplace transform domain using the correspondence principle and is valid for any linear constitutive relationship between stress and strain. The specific implementation described in this paper is a semi-analytic discretization method which assumes isotropic elastic structure and a Maxwell constitutive relation. It accounts for viscoelastic-gravitational coupling under lateral variations in elastic parameters and viscosity. For a given viscoelastic structure and minimum wavelength scale, the computational effort involved with the numerical algorithm is proportional to the volume of the laterally heterogeneous region. Examples are presented of the calculation of post-seismic relaxation with a shallow, laterally heterogeneous volume following synthetic impulsive seismic events, and they illustrate the potentially large effect of regional 3-D heterogeneities on regional deformation patterns.

  19. Corresponding Relation Between the Space-time Evolution of Seismic Apparent Strain and the Region of Strong Earthquakes in Yunnan

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    On the basis of our predecessors' research, we study the distribution and the space-time evolution characteristics of the seismic apparent strain field in Yunnan since the 1970's using the seismic data of Yunnan and its surrounding areas. The result shows that there is arather strong corresponding relationship between the anomaly region of seismic apparent strain and strong earthquakes. In the nine earthquakes studied, anomaly areas of seismic apparent strain had appeared before eight earthquakes, including five occurring in the anomaly region and three on the edge. Finally, the investigative result is demonstrated primarily.

  20. On the development of a seismic source zonation model for seismic hazard assessment in western Saudi Arabia

    Science.gov (United States)

    Zahran, Hani M.; Sokolov, Vladimir; Roobol, M. John; Stewart, Ian C. F.; El-Hadidy Youssef, Salah; El-Hadidy, Mahmoud

    2016-07-01

    A new seismic source model has been developed for the western part of the Arabian Peninsula, which has experienced considerable earthquake activity in the historical past and in recent times. The data used for the model include an up-to-date seismic catalog, results of recent studies of Cenozoic faulting in the area, aeromagnetic anomaly and gravity maps, geological maps, and miscellaneous information on volcanic activity. The model includes 18 zones ranging along the Red Sea and the Arabian Peninsula from the Gulf of Aqaba and the Dead Sea in the north to the Gulf of Aden in the south. The seismic source model developed in this study may be considered as one of the basic branches in a logic tree approach for seismic hazard assessment in Saudi Arabia and adjacent territories.

  1. Statistical analysis on energy field of seismicity in Ningxia and its neighborhood region

    Institute of Scientific and Technical Information of China (English)

    杨明芝; 赵卫明

    2004-01-01

    The random function theory is used in the paper. Taking the regional seismicity energy as the random function of space and time, the features of small seismicity field in Ningxia and its neighborhood region are studied by the analytical method of natural orthogonal function expansion. The chief part of the field, i.e., the temporal changes of time "weight"coefficients of first several typical fields is analyzed. We have found that their values had upward and downward changes of a large amplitude before moderate-strong earthquakes and showed variation features correlating to moderate-strong earthquakes occurred in the region and its surrounding areas. From the earthquake examples in Ningxia region, we can make the conclusion that the method of natural orthogonal function expansion of earthquake energy stochastic field is an earthquake analysis and prediction method that is worth further exploration.

  2. Compilation of the GSHAP regional seismic hazard for Europe, Africa and the Middle East

    Directory of Open Access Journals (Sweden)

    D. Mayer-Rosa

    1999-06-01

    Full Text Available The seismic hazard map of the larger Europe-Africa-Middle East region has been generated as part of the global GSHAP hazard map. The hazard, expressing Peak Ground Acceleration (PGA expected at 10% probability of exceedance in 50 years, is obtained by combining the results of 16 independent regional and national projects; among these is the hazard assessment for Libya and for the wide sub-Saharan Western African region, specifically produced for this regional compilation and here discussed to some length. Features of enhanced seismic hazard are observed along the African rift zone and in the Alpine-Himalayan belt, where there is a general eastward increase in hazard with peak levels in Greece, Turkey, Caucasus and Iran.

  3. Identification of temporal patterns in the seismicity of Sumatra using Poisson Hidden Markov models

    Directory of Open Access Journals (Sweden)

    Katerina Orfanogiannaki

    2014-05-01

    Full Text Available On 26 December 2004 and 28 March 2005 two large earthquakes occurred between the Indo-Australian and the southeastern Eurasian plates with moment magnitudes Mw=9.1 and Mw=8.6, respectively. Complete data (mb≥4.2 of the post-1993 time interval have been used to apply Poisson Hidden Markov models (PHMMs for identifying temporal patterns in the time series of the two earthquake sequences. Each time series consists of earthquake counts, in given and constant time units, in the regions determined by the aftershock zones of the two mainshocks. In PHMMs each count is generated by one of m different Poisson processes that are called states. The series of states is unobserved and is in fact a Markov chain. The model incorporates a varying seismicity rate, it assigns a different rate to each state and it detects the changes on the rate over time. In PHMMs unobserved factors, related to the local properties of the region are considered affecting the earthquake occurrence rate. Estimation and interpretation of the unobserved sequence of states that underlie the data contribute to better understanding of the geophysical processes that take place in the region. We applied PHMMs to the time series of the two mainshocks and we estimated the unobserved sequences of states that underlie the data. The results obtained showed that the region of the 26 December 2004 earthquake was in state of low seismicity during almost the entire observation period. On the contrary, in the region of the 28 March 2005 earthquake the seismic activity is attributed to triggered seismicity, due to stress transfer from the region of the 2004 mainshock.

  4. Exploring Large-Scale Cross-Correlation for Teleseismic and Regional Seismic Event Characterization

    Science.gov (United States)

    Hauk, T. F.; Dodge, D. A.; Addair, T.; Walter, W. R.; Myers, S. C.; Ford, S. R.; Harris, D. B.; Ruppert, S. D.

    2013-12-01

    The decrease in cost of digital storage space and computation power invites new methods of seismic data processing. At Lawrence Livermore National Laboratory (LLNL), we operate a research database of seismic events and waveforms for nuclear explosion monitoring and other applications. The LLNL database contains several million events associated with more than 330 million waveforms at thousands of stations. We are using this database to explore the power of seismic waveform correlation to quantify signal similarities, to discover new events not in catalogs, and to more accurately locate events and identify source types. The results presented here are preliminary, and apply mostly to a subset of seismicity in Eurasia and North America. Much more remains to be done to understand and make use of these results. We computed the waveform correlation for event pairs in the LLNL database in 15 frequency bands and for 8 phase windows. The correlation coefficient exceeds 0.6 for over 370 million waveform pairs. Overall, about 16% of the events in our waveform database correlate with one or more events on at least one channel. However, at very short distances, this number rises to as high as 55%. At distances > 20 degrees the percent of correlated events ranges from ~1% to 10%. The majority of correlated waveforms are found at relatively small (mining seismicity. We are also looking for regional variations and event-type variations in the relation between event-station separation and correlation value.

  5. Seismic patterns of the Guerrero-Oaxaca, Mexico region, and its relationship to the continental margin structure

    Science.gov (United States)

    Yamamoto, Jaime; González-Moran, Tomas; Quintanar, Luis; Zavaleta, Ana B.; Zamora, Araceli; Espindola, Victor H.

    2013-01-01

    The main purpose of this paper is to enhance awareness on the seismic evidences that suggest a possible segmentation of the continental margin at the Guerrero-Oaxaca, Mexico region. Data from a recent 7 months survey of microseismicity carried out from 2008 December to 2009 June at Ometepec, Guerrero area, using a portable broad-band digital seismographs network added with data of a previous survey and the aftershocks distribution of the 1982 and 1995 major earthquakes permit to infer the characteristics of the seismic patterns of the Acapulco-Pinotepa Nacional portion of the southern Mexico subduction region. Two different seismic regimens are apparent, one in the Acapulco-Marquelia and the other in the Marquelia-Pinotepa Nacional areas. In the Acapulco-Marquelia portion, the seismicity is broader and dispersed starting at the coast up to 160 km inland approximately. Seismicity in the Marquelia-Pinotepa portion, on the other hand, is narrower and concentrates near the coast. The two seismic regimens are separated by a narrow band or strip of low seismic activity, nearly perpendicular to the coast and trench axis. The apparent low seismicity strip that separates the seismic regimens may trace the position either of a seismically inactive fracture zone or a seismic gap. Moreover, careful observation of the epicentres distribution of the Marquelia-Pinotepa segment reveals two clusters of events separated by another low seismicity strip. Thus, the two observed low activity strips, located near the northern tip of the Ometepec submarine canyon and Punta Maldonado, respectively, are interpreted in this paper as corresponding to disruptions of the continental margin. Other low seismic activity strips probably exist but these two are the most conspicuous. Supplementary information on fault mechanisms available for this area seems to substantiate additionally this interpretation. The observations reported are important to understand the mechanics of the major earthquakes

  6. The effect of pore fluid on seismicity: a computer model

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The influence of fluid on seismicity of a computerized system is analyzed in this paper. The diffusion equation of fluid in a crustal fault area is developed and used in the calculation of a spring-slide-damper model. With mirror imagin boundary condition and three initial conditions, the equation is solved for a dynamic model that consists of six seismic belts and eight seismogenous sources in each belt with both explicit algorithm and implicit algorithm. The analysis of the model with water sources shows that the implicit algorithm is better to be used to calculate the model. Taking a constant proportion of the pore pressure of a broken element to that of its neighboring elements, the seismicity of the model is calculated with mirror boundary condition and no-water-source initial condition. The results shows that the frequency and magnitude of shocks are both higher than those in the model with no water pore pressure, which provides more complexity to earthquake prediction.

  7. Materials for the investigation of The Seismicity Of Algeria And Adjacent Regions during the twentieth century

    Directory of Open Access Journals (Sweden)

    D. Benouar

    1994-06-01

    Full Text Available Dr. Benouar presents a full and integrated study of the recent seismicity of Algeria and adjacent regions during the twentieth century. He has amassed an impressive amount of macroseismic information pertaining to individual earthquakes, which he combines with instrumental information to reassess the origin parameters of each event. In any compilation of earthquakes it is the additional information beyond the bare accumulation of figures and facts that adds interest and social understanding to the scientific appreciation of the earthquakes themselves. For this it is necessary to know the local conditions, and Dr. Benouar brings out for us very vivid1y the differences between reporting procedures at different times this century, and the ensuing difficulties. It would be most difficult for an outsider to gather the information he presents, and he makes good use of his knowledge of his native land, as well as his professional training as an engineer. We thus learn of the reluctance of the colonial powers to report on damage or casualties outside those inflicted on the expatriate community, and the general difficulties of finding information about earthquakes that occurred during the wars of independence, at a time when effects of even major earthquakes were sometimes minor compared to those of the war itself. He also does not spare us details of political difficulties that arose during periods of reconstruction following recent earthquakes. This work is not restricted, however, to description. He examines the underlying tectonics of the area and deduces estimates of hazard and risk in various parts of the country. He then proceeds to examine the engineering consequences and discuss future needs for building codes and civil protection. Dr. Benouar has produced a work which could well form a model for those wishing to undertake comprelzensive studies of seismicity of other areas, and the measures needed to reduce the effects of catastrophic

  8. An improved multidirectional velocity model for micro-seismic monitoring in rock engineering

    Institute of Scientific and Technical Information of China (English)

    李健; 吴顺川; 高永涛; 李莉洁; 周喻

    2015-01-01

    An improved multidirectional velocity model was proposed for more accurately locating micro-seismic events in rock engineering. It was assumed that the stress wave propagation velocities from a micro-seismic source to three nearest monitoring sensors in a sensor’s array arrangement were the same. Since the defined objective function does not require pre-measurement of the stress wave propagation velocity in the field, errors from the velocity measurement can be avoided in comparison to three traditional velocity models. By analyzing 24 different cases, the proposed multidirectional velocity model iterated by the Simplex method is found to be the best option no matter the source is within the region of the sensor’s array or not. The proposed model and the adopted iterative algorithm are verified by field data and it is concluded that it can significantly reduce the error of the estimated source location.

  9. 3-D seismic tomography of the lithosphere and its geodynamic implications beneath the northeast India region

    Science.gov (United States)

    Raoof, J.; Mukhopadhyay, S.; Koulakov, I.; Kayal, J. R.

    2017-05-01

    We have evolved 3-D seismic velocity structures in northeast India region and its adjoining areas to understand the geodynamic processes of Indian lithosphere that gently underthrusts under the Himalayas and steeply subducts below the Indo-Burma Ranges. The region is tectonically buttressed between the Himalayan arc to the north and the Indo-Burmese arc to the east. The tomographic image shows heterogeneous structure of lithosphere depicting different tectonic blocks. Though our results are limited to shallower depth (0-90 km), it matches well with the deeper continuation of lithospheric structure obtained in an earlier study. We observe low-velocity structure all along the Eastern Himalayas down to 70 km depth, which may be attributed to deeper roots/thicker crust developed by underthrusting of Indian plate. Parallel to this low-velocity zone lies a high-velocity zone in foredeep region, represents the Indian lithosphere. The underthrusting Indian lithosphere under the Himalayas as well as below the Indo-Burma Ranges is well reflected as a high-velocity dipping structure. The buckled up part of bending Indian plate in study region, the Shillong Plateau-Mikir Hills tectonic block, is marked as a high-velocity structure at shallower depth. The Eastern Himalayan Syntaxis, tectonic block where the two arcs meet, is identified as a high-velocity structure. The Bengal Basin, tectonic block to the south of Shillong Plateau, shows low velocity due to its thicker sediments. Based on the tomographic image, a schematic model is presented to elucidate the structure and geodynamics of Indian lithosphere in study region.

  10. A high-resolution ambient seismic noise model for Europe

    Science.gov (United States)

    Kraft, Toni

    2014-05-01

    measurement precision (i.e. earthquake location), while considering this extremely complex boundary condition. To solve this problem I have developed a high-resolution ambient seismic noise model for Europe. The model is based on land-use data derived from satellite imagery by the EU-project CORINE in a resolution of 100x100m. The the CORINE data consists of several land-use classes, which, besides others, contain: industrial areas, mines, urban fabric, agricultural areas, permanent corps, forests and open spaces. Additionally, open GIS data for highways, and major and minor roads and railway lines were included from the OpenStreetMap project (www.openstreetmap.org). This data was divided into three classes that represent good, intermediate and bad ambient conditions of the corresponding land-use class based on expert judgment. To account for noise propagation away from its source a smoothing operator was applied to individual land-use noise-fields. Finally, the noise-fields were stacked to obtain an European map of ambient noise conditions. A calibration of this map with data of existing seismic stations Europe allowed me to estimate the expected noise level in actual ground motion units for the three ambient noise condition classes of the map. The result is a high-resolution ambient seismic noise map, that allows the network designer to make educated predictions on the expected noise level for arbitrary location in Europe. The ambient noise model was successfully tested in several network optimization projects in Switzerland and surrounding countries and will hopefully be a valuable contribution to improving the data quality of microseismic monitoring networks in Europe.

  11. The importance of structural model availability on seismic interpretation

    Science.gov (United States)

    Alcalde, Juan; Bond, Clare E.; Johnson, Gareth; Butler, Robert W. H.; Cooper, Mark A.; Ellis, Jennifer F.

    2017-04-01

    Interpretation of faults in seismic images is central to the creation of geological models of the subsurface. The use of prior knowledge acquired through learning allows interpreters to move from singular observations to reasoned interpretations based on the conceptual models available to them. The amount and variety of fault examples available in textbooks, articles and training exercises is therefore likely to be a determinant factor in the interpreters' ability to interpret realistic fault geometries in seismic data. We analysed the differences in fault type and geometry interpreted in seismic data by students before and after completing a masters module in structural geology, and compared them to the characteristics of faults represented in the module and textbooks. We propose that the observed over-representation of normal-planar faults in early teaching materials influences the interpretation of data, making this fault type and geometry dominant in the pre-module interpretations. However, when the students were exposed to a greater range in fault models in the module, the range of fault type and geometry increased. This work explores the role of model availability in interpretation and advocates for the use of realistic fault models in training materials.

  12. Multiparametric data analysis for seismic sources identification in the Campania re-gion: merge of seismological, structural and gravimetric data.

    OpenAIRE

    G. Gaudiosi; G. Alessio; M. Fedi; G. Florio; R.; Nappi; Luiso, P.; Ricciolino, P.

    2010-01-01

    The Campania region is one of the Italian most active areas from a geodynamic point of view since it is characterized by occurrence of intense and widely spread seismic activity. The seismicity of the area is concentrated mainly along the Southern Apennines chain, as well as beneath the Campanian volcanic areas (Vesuvio, Campi Flegrei, Ischia) and is also originated by seismic sources buried in the Campanian Plain and offshore the Thyrrenian sea. The aim of this paper is an attempt to better ...

  13. Crustal deformation and seismic measurements in the region of McDonald Observatory, West Texas. [Texas and Northern Chihuahua, Mexico

    Science.gov (United States)

    Dorman, H. J.

    1981-01-01

    The arrival times of regional and local earthquakes and located earthquakes in the Basin and Range province of Texas and in the adjacent areas of Chihuahua, Mexico from January 1976 to August 1980 at the UT'NASA seismic array are summarized. The August 1931 Texas earthquake is reevaluated and the seismicity and crustal structure of West Texas is examined. A table of seismic stations is included.

  14. Precursory seismicity in regions of low strain rate: Insights from a physics-based earthquake23 simulator

    Science.gov (United States)

    Christophersen, Annemarie; Rhoades, David A.; Colella, Harmony V.

    2017-03-01

    The well-established earthquake forecasting model 'Every Earthquake a Precursor According to Scale' (EEPAS) is based on the observation that the magnitude and rate of minor earthquakes increases prior to large earthquakes. The precursor time is measured between this increase and the mainshock and is in the order of months to decades. Fitting the EEPAS model to different regional earthquake catalogues has indicated that the precursor time is longer in more slowly deforming tectonic environments. Examples from the stable continental region of Australia confirm this. To overcome the challenge of limited earthquake records in the analysis of the precursor time for areas with low strain rate, we use the physics-based earthquake simulator, RSQSim to generate a series of synthetic earthquake catalogues. A fault network with realistic complexity, is employed, based on the Wellington, New Zealand, fault network. The slip rates on faults are systematically reduced by five successive factors of 1/4. Fitting the EEPAS model to these synthetic catalogues shows that the precursor time is inversely proportional to the reduction in slip rate. Results suggest that the expected precursor times for large earthquakes in stable continental regions far exceed the length of available catalogues. The expected precursor time for the 2010 M7.1 Darfield, New Zealand, earthquake, which apparently had no precursory seismicity in the instrumental catalogue, also exceeds the length of the available catalogue. Therefore, applying the EEPAS model to physics-based simulators allows us to start understanding the phenomenon of precursory seismicity.

  15. Dynamics of multifractal and correlation characteristics of the spatio-temporal distribution of regional seismicity before the strong earthquakes

    Directory of Open Access Journals (Sweden)

    D. Kiyashchenko

    2003-01-01

    Full Text Available Investigations of the distribution of regional seismicity and the results of numerical simulations of the seismic process show the increase of inhomogenity in spatio-temporal distribution of the seismicity prior to large earthquakes and formation of inhomogeneous clusters in a wide range of scales. Since that, the multifractal approach is appropriate to investigate the details of such dynamics. Here we analyze the dynamics of the seismicity distribution before a number of strong earthquakes occurred in two seismically active regions of the world: Japan and Southern California. In order to study the evolution of spatial inhomogeneity of the seismicity distribution, we consider variations of two multifractal characteristics: information entropy of multifractal measure generation process and the higher-order generalized fractal dimension of the continuum of the earthquake epicenters. Also we studied the dynamics of the level of spatio-temporal correlations in the seismicity distribution. It is found that two aforementioned multifractal characteristics tend to decrease and the level of spatio-temporal correlations tends to increase before the majority of considered strong earthquakes. Such a tendency can be considered as an earthquake precursory signature. Therefore, the results obtained show the possibility to use multifractal and correlation characteristics of the spatio-temporal distribution of regional seismicity for seismic hazard risk evaluation.

  16. Regionalizing global climate models

    NARCIS (Netherlands)

    Pitman, A.J.; Arneth, A.; Ganzeveld, L.N.

    2012-01-01

    Global climate models simulate the Earth's climate impressively at scales of continents and greater. At these scales, large-scale dynamics and physics largely define the climate. At spatial scales relevant to policy makers, and to impacts and adaptation, many other processes may affect regional and

  17. Regionalizing global climate models

    NARCIS (Netherlands)

    Pitman, A.J.; Arneth, A.; Ganzeveld, L.N.

    2012-01-01

    Global climate models simulate the Earth's climate impressively at scales of continents and greater. At these scales, large-scale dynamics and physics largely define the climate. At spatial scales relevant to policy makers, and to impacts and adaptation, many other processes may affect regional and

  18. Dense seismic networks as a tool to characterize active faulting in regions of slow deformation

    Science.gov (United States)

    Custódio, Susana; Arroucau, Pierre; Carrilho, Fernando; Cesca, Simone; Dias, Nuno; Matos, Catarina; Vales, Dina

    2016-04-01

    The theory of plate tectonics states that the relative motion between lithospheric plates is accommodated at plate boundaries, where earthquakes occur on long faults. However, earthquakes with a wide range of magnitudes also occur both off plate boundaries, in intra-plate settings, and along discontinuous, diffuse plate boundaries. These settings are characterized by low rates of lithospheric deformation. A fundamental limitation in the study of slowly deforming regions is the lack of high-quality observations. In these regions, earthquake catalogs have traditionally displayed diffuse seismicity patterns. The location, geometry and activity rate of faults - all basic parameters for understanding fault dynamics - are usually poorly known. The dense seismic networks deployed in the last years around the world have opened new windows in observational seismology. Although high-magnitude earthquakes are rare in regions of slow deformation, low-magnitude earthquakes are well observable on the time-scale of these deployments. In this presentation, we will show how data from dense seismic deployments can be used to characterize faulting in regions of slow deformation. In particular, we will present the case study of western Iberia, a region undergoing low-rate deformation and which has generated some of the largest earthquakes in Europe, both intraplate (mainland) and interplate (offshore). The methods that we employ include automated earthquake detection methods to lower the completeness magnitude of catalogs, earthquake relocations, focal mechanisms patterns, waveform similarity and clustering analysis.

  19. Seismic reflection survey at Llancanelo region (Mendoza, Argentina) and preliminary interpretation of Neogene stratigraphic features

    Science.gov (United States)

    Osella, A.; Onnis, L.; de la Vega, M.; Tassone, A.; Violante, R. A.; Lippai, H.; López, E.; Rovere, E. I.

    2015-07-01

    A shallow multichannel seismic survey reaching depths of 700/800 m was performed for the first time in the Llancanelo Lake region (Southern Mendoza Province, Argentina), in order to depict the major Neogene sedimentary-volcanic sequences that form the final infilling of the tectonic-volcanic basin where the lake is located. The seismic survey advances on the results of previous geoelectric and electromagnetic surveys carried out at early stages of the research that reached the uppermost 80-100 m of the sequences (Quaternary), and therefore they go deeper in the subsoil. All the surveys were supported by surface and subsoil geological observations. After explaining the details of the performed seismic methodology, the obtained results are discussed, which indicate the presence of three major sedimentary units with increasing volcanic (basaltic layers) intercalations with depth, that accommodate to the geometry of the depocenter. The entire sequence encompasses most of the Neogene. This research sets the methodological basis for future, more detailed shallow seismic surveys in the region.

  20. VELOCITIES OF SLOW MIGRATION OF SEISMIC ACTIVITY IN CIS-BAIKAL REGION

    Directory of Open Access Journals (Sweden)

    Anna V. Novopashina

    2015-09-01

    Full Text Available Three-dimensional space-time diagrams of «logarithm of total energy released by earthquakes» parameter, lgEsum are constructed for regions with stable concentrations of earthquake epicenters in Cis-Baikal region for a period from 1964 to 2002. Based on analyses of such diagrams, areas of slow migration of seismic activity are defined. Estimated are distances, time and velocities of slow migration in the range of the first kilometers – first dozen of kilometers per year.Procedures of seismic data projection and construction of 3D diagrams are described in brief. A general scheme including contours of projection areas is proposed for the Pribaikalie (Fig. 1.Three space-time diagrams are presented as examples of application of the above mentioned procedures. They are constructed for the Middle and Southern Baikal basins and the western part of the NE flank of the Baikal rift system (Fig. 2. Integrated analytical results are presented for all the diagrams which record earthquake migration within the Baikal rift system.We also present a scheme of the zone of slow migrations ranked by dominating velocities (Fig. 3 and a diagram of the migration velocity range. We consider possible causes of slow migration of seismic activity at variable velocities: (1 slow deformation waves spreading in the crust, and (2 independent propagation of the deformation front along active faults.Regulations of migration of strong earthquakes can be useful for definition of timelines and locations of future strong seismic events.

  1. Adaptive finite difference for seismic wavefield modelling in acoustic media.

    Science.gov (United States)

    Yao, Gang; Wu, Di; Debens, Henry Alexander

    2016-08-05

    Efficient numerical seismic wavefield modelling is a key component of modern seismic imaging techniques, such as reverse-time migration and full-waveform inversion. Finite difference methods are perhaps the most widely used numerical approach for forward modelling, and here we introduce a novel scheme for implementing finite difference by introducing a time-to-space wavelet mapping. Finite difference coefficients are then computed by minimising the difference between the spatial derivatives of the mapped wavelet and the finite difference operator over all propagation angles. Since the coefficients vary adaptively with different velocities and source wavelet bandwidths, the method is capable to maximise the accuracy of the finite difference operator. Numerical examples demonstrate that this method is superior to standard finite difference methods, while comparable to Zhang's optimised finite difference scheme.

  2. Integration of onshore and offshore seismological data to study the seismicity of the Calabrian Region

    Science.gov (United States)

    D'Alessandro, Antonino; Guerra, Ignazio; D'Anna, Giuseppe; Gervasi, Anna; Harabaglia, Paolo; Luzio, Dario; Stellato, Gilda

    2014-05-01

    The Pollino Massif marks the transition from the Southern Appenninic to the Calabrian Arc. On the western side it is characterized by a moderately sized seismicity (about 9 M > 4 events in the last 50 years), well documented in the last 400 years. The moment tensor solutions available in this area yields, mainly, normal faults with coherent Southern Appeninic trend. This remains true also for the events that are localized on the calabrian side of Pollino, South of the massif. In most of the Sibari plane, seismic activity is very scarce, while it is again rather marked on its southeastern corner, both onshore and offshore. The above observations point to the perspective that the stress field of a vast portion of Northern Calabria still resembles that of the Southern Appenines. In this frame, it becomes important to investigate the offshore seismicity of the Sibari Gulf and the deformation pattern within the Sibari Plane. The latter might function as a hinge to transfer the deformation of the extensional fault system in the Pollino area to a different offshore fault system. Since return times of larger events might be very long, we need to investigate the true seismic potential of the offshore faults and to verify whether they are truly strike slip or if they could involve relevant thrust or normal components, that would add to the risk that of potentially associated tsunamis. Despite their importance in the understanding of the seismotectonic processes taking place in the Southern Appenninic - Calabrian Arc border and surrounding areas, the seismicity and the seismogenic volumes of the Sibari Gulf until now has not been well characterized due to the lack of offshore seismic stations. The seismicity of the Calabrian is monitored by the Italian National Seismic Network (INSN) managed by Istituto Nazionale di Geofisica e Vulcanologia and by the Calabrian Regional Seismic Network (CRSN) managed by the University of Calabria. Both the network comprise only on

  3. The imprint of crustal density heterogeneities on regional seismic wave propagation

    Science.gov (United States)

    Płonka, Agnieszka; Blom, Nienke; Fichtner, Andreas

    2016-11-01

    Density heterogeneities are the source of mass transport in the Earth. However, the 3-D density structure remains poorly constrained because travel times of seismic waves are only weakly sensitive to density. Inspired by recent developments in seismic waveform tomography, we investigate whether the visibility of 3-D density heterogeneities may be improved by inverting not only travel times of specific seismic phases but complete seismograms.As a first step in this direction, we perform numerical experiments to estimate the effect of 3-D crustal density heterogeneities on regional seismic wave propagation. While a finite number of numerical experiments may not capture the full range of possible scenarios, our results still indicate that realistic crustal density variations may lead to travel-time shifts of up to ˜ 1 s and amplitude variations of several tens of percent over propagation distances of ˜ 1000 km. Both amplitude and travel-time variations increase with increasing epicentral distance and increasing medium complexity, i.e. decreasing correlation length of the heterogeneities. They are practically negligible when the correlation length of the heterogeneities is much larger than the wavelength. However, when the correlation length approaches the wavelength, density-induced waveform perturbations become prominent. Recent regional-scale full-waveform inversions that resolve structure at the scale of a wavelength already reach this regime.Our numerical experiments suggest that waveform perturbations induced by realistic crustal density variations can be observed in high-quality regional seismic data. While density-induced travel-time differences will often be small, amplitude variations exceeding ±10 % are comparable to those induced by 3-D velocity structure and attenuation. While these results certainly encourage more research on the development of 3-D density tomography, they also suggest that current full-waveform inversions that use amplitude

  4. Internal stress field at Mount Vesuvius: A model for background seismicity at a central volcano

    Science.gov (United States)

    de Natale, Giuseppe; Petrazzuoli, Stefano M.; Troise, Claudia; Pingue, Folco; Capuano, Paolo

    2000-07-01

    We propose a model to explain the background seismicity occurring at Somma-Vesuvius in its present, mostly quiescent period. A finite element procedure has been used to simulate the stress field due to gravitational body forces in an axisymmetric volcano characterized by a central high-rigidity anomaly. Results emphasize the important effect of axial high-rigidity, which concentrates at its borders stresses resulting from the gravitational load of the volcanic edifice, as well as external (regional) stresses. The joint effect of the gravitational loading and of the presence of the anomaly produces stresses very close to or above the critical rupture threshold. The observed spatial concentrations of seismicity and moment release correlate well with peaks of computed maximum shear stress. Seismicity is then interpreted as due to small stress perturbations concentrated around the high-rigidity core and added to a system already close, to the failure threshold. This model can explain the widely observed occurrence of background seismicity at central volcanoes worldwide.

  5. The estimation of yearly probability gain for seismic statistical model

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on the calculation method of information gain in the stochastic process presented by Vere-Jones, the relation between information gain and probability gain is studied, which is very common in earthquake prediction, and the yearly probability gain for seismic statistical model is proposed. The method is applied to the non-stationary Poisson model with whole-process exponential increase and stress release model. In addition, the prediction method of stress release model is obtained based on the inverse function simulation method of stochastic variable.

  6. Study on the Determination of the Significant National Seismic Monitoring and Protection Regions

    Institute of Scientific and Technical Information of China (English)

    Zhang Guomin; Fu Zhengxiang; Wang Xiaoqing; Liu Guiping

    2007-01-01

    The paper describes firstly the principies and scientific train of thought involved in determining the significant seismic monitoring and protection regions (SSMPR) in China.The principles include the gradation principle, i.e.the national level SSMPR and the provincial level SSMPR,the principle of highlighting priorities,namely,the area of an SSMPR should be a fraction of the total area of the country or of the respective province,but the earthquake losses incurred in SSMPR should be a major proportion of the national or provincial ones.The scientific train of thought adopted is to determine the SSMPR on the basis of seismic hazard assessment and loss estimation.Secondly,it reviews the achievements in determining the SSMPRs for the period from 1996 to 2005.The result shows that 10 strong earthquakes occurred during that period in the areas with earthquake monitoring and prediction capability available on the Chinese continent, 8 of which occurred in SSMPRs with the economic loss and death toll accounting for 67% and 92% of the total loss on the Chinese mainland.Lastly,the paper introduces preparatory research for determining the SSMPR for the period from 2006 to 2020,including decade-scale mid-and long-range seismic risk assessment based on seismology,seismogeology,geodesy,earthquake engineering,sociology and stochastics and so on,and the national seismic risk probability map,the seismic hazard (intensity) map,earthquake disaster losses map and the comprehensive seismic risk index,etc.obtained for the period of 2006 to 2020.

  7. Performance assessment of models to forecast induced seismicity

    Science.gov (United States)

    Wiemer, Stefan; Karvounis, Dimitrios; Zechar, Jeremy; Király, Eszter; Kraft, Toni; Pio Rinaldi, Antonio; Catalli, Flaminia; Mignan, Arnaud

    2015-04-01

    Managing and mitigating induced seismicity during reservoir stimulation and operation is a critical prerequisite for many GeoEnergy applications. We are currently developing and validating so called 'Adaptive Traffic Light Systems' (ATLS), fully probabilistic forecast models that integrate all relevant data on the fly into a time-dependent hazard and risk model. The combined model intrinsically considers both aleatory and model-uncertainties, the robustness of the forecast is maximized by using a dynamically update ensemble weighting. At the heart of the ATLS approach are a variety of forecast models that range from purely statistical models, such as flow-controlled Epidemic Type Aftershock Sequence (ETAS) models, to models that consider various physical interaction mechanism (e.g., pore pressure changes, dynamic and static stress transfer, volumetric strain changes). The automated re-calibration of these models on the fly given data imperfection, degrees of freedom, and time-constraints is a sizable challenge, as is the validation of the models for applications outside of their calibrated range (different settings, larger magnitudes, changes in physical processes etc.). Here we present an overview of the status of the model development, calibration and validation. We also demonstrate how such systems can contribute to a quantitative risk assessment and mitigation of induced seismicity in a wide range of applications and time scales.

  8. Dike propagation energy balance from deformation modeling and seismic release

    Science.gov (United States)

    Bonaccorso, Alessandro; Aoki, Yosuke; Rivalta, Eleonora

    2017-06-01

    Magma is transported in the crust mainly by dike intrusions. In volcanic areas, dikes can ascend toward the free surface and also move by lateral propagation, eventually feeding flank eruptions. Understanding dike mechanics is a key to forecasting the expected propagation and associated hazard. Several studies have been conducted on dike mechanisms and propagation; however, a less in-depth investigated aspect is the relation between measured dike-induced deformation and the seismicity released during its propagation. We individuated a simple x that can be used as a proxy of the expected mechanical energy released by a propagating dike and is related to its average thickness. For several intrusions around the world (Afar, Japan, and Mount Etna), we correlate such mechanical energy to the seismic moment released by the induced earthquakes. We obtain an empirical law that quantifies the expected seismic energy released before arrest. The proposed approach may be helpful to predict the total seismic moment that will be released by an intrusion and thus to control the energy status during its propagation and the time of dike arrest.type="synopsis">type="main">Plain Language SummaryDike propagation is a dominant mechanism for magma ascent, transport, and eruptions. Besides being an intriguing physical process, it has critical hazard implications. After the magma intrusion starts, it is difficult to predict when and where a specific horizontal dike is going to halt and what its final length will be. In our study, we singled an equation that can be used as a proxy of the expected mechanical energy to be released by the opening dike. We related this expected energy to the seismic moment of several eruptive intrusions around the world (Afar region, Japanese volcanoes, and Mount Etna). The proposed novel approach is helpful to estimate the total seismic moment to be released, therefore allowing potentially predicting when the dike will end its propagation. The approach helps

  9. Poroelastic modeling of seismic boundary conditions across a fracture.

    Science.gov (United States)

    Nakagawa, Seiji; Schoenberg, Michael A

    2007-08-01

    Permeability of a fracture can affect how the fracture interacts with seismic waves. To examine this effect, a simple mathematical model that describes the poroelastic nature of wave-fracture interaction is useful. In this paper, a set of boundary conditions is presented which relate wave-induced particle velocity (or displacement) and stress including fluid pressure across a compliant, fluid-bearing fracture. These conditions are derived by modeling a fracture as a thin porous layer with increased compliance and finite permeability. Assuming a small layer thickness, the boundary conditions can be derived by integrating the governing equations of poroelastic wave propagation. A finite jump in the stress and velocity across a fracture is expressed as a function of the stress and velocity at the boundaries. Further simplification for a thin fracture yields a set of characteristic parameters that control the seismic response of single fractures with a wide range of mechanical and hydraulic properties. These boundary conditions have potential applications in simplifying numerical models such as finite-difference and finite-element methods to compute seismic wave scattering off nonplanar (e.g., curved and intersecting) fractures.

  10. Seismicity pattern and thermal anomalies in the southern Baltic region before and during the Kaliningrad earthquakes of 2004

    Science.gov (United States)

    Nikonov, A. A.

    2008-11-01

    The seismic situation in the SE Baltic region that existed during the period 1990-2006, including the unexpectedly strong Kaliningrad earthquakes of 2004, is analyzed. The spatiotemporal variation of seismic events in the region is examined on the basis of a newly compiled catalog of tectonic earthquakes. The analysis revealed outbursts of seismic activity in 1995 and 2004, structurization of the distribution of shocks, and their southward migration. The distribution of hot springs that arose in 2002-2004 is analyzed in relation to seismological data. The seismic process and thermal anomalies are shown to be geodynamically controlled, which provided constraints on the nucleation process and focal mechanism of the Kaliningrad earthquakes. The region, located in the western East European platform, should be regarded as seismically rather active.

  11. Seismic Modeling of the Alasehir Graben, Western Turkey

    Science.gov (United States)

    Gozde Okut, Nigar; Demirbag, Emin

    2014-05-01

    The purpose of this study is to develop a depth model to make synthetic seismic reflection sections, such as stacked and migrated sections with different velocity models. The study area is east-west trending Alasehir graben which is one of the most prominent structure in the western Anatolia, proved to have geothermal energy potential by researchers and exploration companies. Geological formations were taken from Alaşehir-1 borehole drilled by Turkish Petroleum Corporation (Çiftçi, 2007) and seismic interval velocities were taken from check-shots in the same borehole (Kolenoǧlu-Demircioǧlu, 2009). The most important structure is the master graben bounding fault (MGBF) in the southern margin of the Alasehir graben. Another main structure is the northern bounding fault called the antithetic fault of the MGBF with high angle normal fault characteristic. MGBF is a crucial contact between sedimentary cover and the metamorphic basement. From basement to the surface, five different stratigraphic units constitute graben fill . All the sedimentary units thicknesses get thinner from the southern margin to the northern margin of the Alasehir graben displaying roll-over geometry. A commercial seismic data software was used during modeling. In the first step, a 2D velocity/depth model was defined. Ray tracing was carried out with diffraction option to produce the reflection travel times. The reflection coefficients were calculated and wavelet shaping was carried out by means of band-pass filtering. Finally synthetic stacked section of the Alasehir graben was obtained. Then, migrated sections were generated with different velocity models. From interval velocities, average and RMS velocities were calculated for the formation entires to test how the general features of the geological model may change against different seismic models after the migration. Post-stack time migration method was used. Pseudo-velocity analysis was applied at selected CDP locations. In theory

  12. Seismic hazard of the Kivu rift (western branch, East African Rift system): new neotectonic map and seismotectonic zonation model

    Science.gov (United States)

    Delvaux, Damien; Mulumba, Jean-Luc; Sebagenzi Mwene Ntabwoba, Stanislas; Fiama Bondo, Silvanos; Kervyn, François; Havenith, Hans-Balder

    2017-04-01

    The first detailed probabilistic seismic hazard assessment has been performed for the Kivu and northern Tanganyika rift region in Central Africa. This region, which forms the central part of the Western Rift Branch, is one of the most seismically active part of the East African rift system. It was already integrated in large scale seismic hazard assessments, but here we defined a finer zonation model with 7 different zones representing the lateral variation of the geological and geophysical setting across the region. In order to build the new zonation model, we compiled homogeneous cross-border geological, neotectonic and sismotectonic maps over the central part of East D.R. Congo, SW Uganda, Rwanda, Burundi and NW Tanzania and defined a new neotectonic sheme. The seismic risk assessment is based on a new earthquake catalogue, compiled on the basis of various local and global earthquake catalogues. The use of macroseismic epicenters determined from felt earthquakes allowed to extend the time-range back to the beginning of the 20th century, spanning 126 years, with 1068 events. The magnitudes have been homogenized to Mw and aftershocks removed. From this initial catalogue, a catalogue of 359 events from 1956 to 2015 and with M > 4.4 has been extracted for the seismic hazard assessment. The seismotectonic zonation includes 7 seismic source areas that have been defined on the basis of the regional geological structure, neotectonic fault systems, basin architecture and distribution of thermal springs and earthquake epicenters. The Gutenberg-Richter seismic hazard parameters were determined using both the least square linear fit and the maximum likelihood method (Kijko & Smit aue program). Seismic hazard maps have been computed with the Crisis 2012 software using 3 different attenuation laws. We obtained higher PGA values (475 years return period) for the Kivu rift region than the previous estimates (Delvaux et al., 2016). They vary laterally in function of the tectonic

  13. Broadband Waveform Modeling to Evaluate the USGS Seismic Velocity Model for the San Francisco Bay Area

    Science.gov (United States)

    Rodgers, A.; Petersson, A.; Nilsson, S.; Sjogreen, B.; McCandless, K.

    2006-12-01

    As part of the 1906 San Francisco earthquake centenary, the USGS developed a three-dimensional seismic velocity and attenuation model for Northern California based on detailed geologic and geophysical constraints. The model was used to predict ground motions for the 1906 rupture. In this study we evaluate the model to assess its ability to accurately predict ground motions from moderate earthquakes recorded on broadband stations. Satisfactory prediction of ground motions from these events will provide hope for accurate modeling of future scenario earthquakes. Simulations were performed on large parallel computer(s) with a new elastic finite difference code developed at LLNL. We simulated broadband ground motions (0-0.25 Hz) for several moderate (magnitude 3.5-5.0) earthquakes in the region observed at Berkeley Digital Seismic Network (BDSN) broadband stations. These events are well located and can be modeled with simple point moment tensor sources (taken from the Berkeley Seismological Laboratory catalog), helping to isolate the effects of structure on the waveforms. These data sample the region's diverse tectonic structures, such as the bay muds, sedimentary basins and hard rock complexes. Preliminary results indicate that the simulations reproduce many important features in the data. For example, observed long duration surface waves are often predicted for complex paths (traveling across contrasting structures) and through sedimentary basins. Excellent waveform fits were frequently obtained for long-period comparisons (0.02-0.1) and good fits were often obtained for shorter periods. We will attempt higher frequency simulations to test the ability of the model to match the high frequency response. Finally, we performed large scenario earthquake simulations for the Hayward Fault. These simulations predict large amplifications across the Santa Clara and San Ramon/Livermore Valley sedimentary basins and with the Sacramento/San Joaquin River Delta.

  14. Plate Motions Predicted from Global Dynamic Models and Seismic Tomography: The Problem of North American Plate Motion

    Science.gov (United States)

    Liu, S.; King, S. D.; Adam, C. M.

    2016-12-01

    Seismic tomography is a snapshot of the mantle convection system and provides important constraints on Earth's internal dynamics. An increasing number of global seismic tomography models along with various rheological structures have been used to compute mantle flow pattern and the resulting surface expressions, including dynamic topography and geoid. Accurately predicting the plate motion from the mantle dynamic models is a challenge particularly with the newest generation of seismic tomography models (e.g., S40RTS, SAVANI), especially for the North American plate which only has a little subduction along it's boundary. The difficulties include the uncertainty of the velocity-to-density scaling, discrepancies between different seismic tomography models, and the computational technology to solve for global mantle flow with observationally constrained high resolution models. We use the code ASPECT (Advanced Solver for Problems in Earth CovecTion) to make a series of tests to derive mantle flow pattern from different global seismic tomography models and rheological structures. We further make a quantitative statistical comparison between the modeled and observed plate motions in terms of flow magnitude, flow direction, and plateness within each plate area. We investigate how the velocity-to-density scaling, the features of seismic tomography models, and the lateral rheological structures of the lithosphere and upper mantle influence the modeled plate motions. We find that the velocity-to-density scaling mainly changes the flow magnitude and has little impact on the flow direction. The results of different seismic tomography models are similar broadly but can be quite different in some regions. The presence of lateral viscosity variations including stiff cratons, weak plate boundary zones, and high viscosity slabs along with density variations from seafloor age and subducting slabs can improve the fit to observed plate motions. With a very small fraction of subduction

  15. Analogue earthquakes and seismic cycles: experimental modelling across timescales

    Science.gov (United States)

    Rosenau, Matthias; Corbi, Fabio; Dominguez, Stephane

    2017-05-01

    Earth deformation is a multi-scale process ranging from seconds (seismic deformation) to millions of years (tectonic deformation). Bridging short- and long-term deformation and developing seismotectonic models has been a challenge in experimental tectonics for more than a century. Since the formulation of Reid's elastic rebound theory 100 years ago, laboratory mechanical models combining frictional and elastic elements have been used to study the dynamics of earthquakes. In the last decade, with the advent of high-resolution monitoring techniques and new rock analogue materials, laboratory earthquake experiments have evolved from simple spring-slider models to scaled analogue models. This evolution was accomplished by advances in seismology and geodesy along with relatively frequent occurrences of large earthquakes in the past decade. This coincidence has significantly increased the quality and quantity of relevant observations in nature and triggered a new understanding of earthquake dynamics. We review here the developments in analogue earthquake modelling with a focus on those seismotectonic scale models that are directly comparable to observational data on short to long timescales. We lay out the basics of analogue modelling, namely scaling, materials and monitoring, as applied in seismotectonic modelling. An overview of applications highlights the contributions of analogue earthquake models in bridging timescales of observations including earthquake statistics, rupture dynamics, ground motion, and seismic-cycle deformation up to seismotectonic evolution.

  16. Anisotropic seismic-waveform inversion: Application to a seismic velocity model from Eleven-Mile Canyon in Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gao, Kai [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Huang, Lianjie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sabin, Andrew [Geothermal Program Office, China Lake, CA (United States)

    2016-03-31

    Accurate imaging and characterization of fracture zones is crucial for geothermal energy exploration. Aligned fractures within fracture zones behave as anisotropic media for seismic-wave propagation. The anisotropic properties in fracture zones introduce extra difficulties for seismic imaging and waveform inversion. We have recently developed a new anisotropic elastic-waveform inversion method using a modified total-variation regularization scheme and a wave-energy-base preconditioning technique. Our new inversion method uses the parameterization of elasticity constants to describe anisotropic media, and hence it can properly handle arbitrary anisotropy. We apply our new inversion method to a seismic velocity model along a 2D-line seismic data acquired at Eleven-Mile Canyon located at the Southern Dixie Valley in Nevada for geothermal energy exploration. Our inversion results show that anisotropic elastic-waveform inversion has potential to reconstruct subsurface anisotropic elastic parameters for imaging and characterization of fracture zones.

  17. Climate services for adapting landslide hazard prevention measures in the Vrancea Seismic Region

    Science.gov (United States)

    Micu, Dana; Balteanu, Dan; Jurchescu, Marta; Sima, Mihaela; Micu, Mihai

    2014-05-01

    The Vrancea Seismic Region is covering an area of about 8 000 km2 in the Romanian Curvature Carpathians and Subcarpathians and it is considered one of Europe's most intensely multi-hazard-affected areas. Due to its geomorphic traits (heterogeneous morphostructural units of flysch mountains and molasse hills and depressions), the area is strongly impacted by extreme hydro-meteorological events which are potentially enhancing the numerous damages inflicted to a dense network of human settlements. An a priori knowledge of future climate change is a useful climate service for local authorities to develop regional adapting strategies and adequate prevention/preparedness frameworks. This paper aims at integrating the results of the high-resolution climate projections over the 21st century (within the FP7 ECLISE project) into the regional landslide hazard assessment. The requirements of users (Civil Protection, Land management, local authorities) for this area refer to reliable and high-resolution spatial data on landslide and flood hazard for short and medium-term risk management strategies. An insight into the future behavior of climate variability in the Vrancea Seismic Region, based on future climate projections of three regional models, under three RCPs (2.6, 4.5, 8.6), suggests a clear warming, both annually and seasonally and a rather limited annual precipitation decrease, but with a strong change of seasonality. A landslide inventory of 2485 cases (shallow and medium seated earth, debris and rock slides and earth and debris flows) was obtained based on large scale geomorphological mapping and aerial photos support (GeoEye, DigitalGlobe; provided by GoogleEarth and BingMaps). The landslides are uniformly distributed across the area, being considered representative for the entire morphostructural environment. Landslide susceptibility map was obtained using multivariate statistical analysis (logistic regression), while a relative landslide hazard index was computed

  18. Geophysical Observatory in Kamchatka region for monitoring of phenomena connected with seismic activity

    Directory of Open Access Journals (Sweden)

    S. Uyeda

    2001-01-01

    Full Text Available Regular monitoring of some geophysical parameters in association with seismicity has been carried out since last year at the Japan-Russian Complex Geophysical Observatory in the Kamchatka region. This observatory was organized in connection with the ISTC project in Russia and was motivated by the results of the FRONTIER/RIKEN and FRONTIER/NASDA research projects in Japan. The main purpose of the observations is to investigate the electromagnetic and acoustic phenomena induced by the lithosphere processes (especially by seismic activity. The seismicity of the Kamchatka area is analyzed and a description of the observatory equipment is presented. At present, the activity of the observatory includes the seismic (frequency range ∆F = 0.5 – 40 Hz and meteorological recordings, together with seismo-acoustic (∆F = 30 – 1000 Hz and electromagnetic observations: three-component magnetic ULF variations ( ∆F = 0.003 – 30 Hz, three-component electric potential variations ( ∆F 1.0 Hz, and VLF transmitter’s signal perturbations ( ∆F ~ 10 – 40 kHz.

  19. Exploring New Boundaries to Mitigate Structural Vibrations of Bridges in Seismic Regions: A Smart Passive Strategy

    Directory of Open Access Journals (Sweden)

    Giuseppe Maddaloni

    2016-01-01

    Full Text Available The combined use of two emerging technologies in the field of seismic engineering is investigated. The first is a semiactive control, to reduce smartly the effects induced by earthquakes on structures. The second is the Seismic Early Warning System which allows an estimate of the Peak Ground Accelerations of an incoming earthquake. This paper proposes the exploitation of this information in the framework of a semiactive control strategy based on the use of magnetorheological (MR dampers. The main idea consists of changing the MR dampers’ behaviour by the PGA estimated by the SEWS, to obtain the optimal seismic response of the structure. The control algorithm needed to drive the variable devices, according to the PGA estimate, is the core issue of the proposed strategy. It has been found that different characteristics of earthquakes that occur at different sites play a significant role in the definition of a control algorithm. Therefore, a design procedure for “regional” control algorithms has been performed. It is based on the results of several nonlinear dynamic simulations performed using natural earthquakes and on the use of a multicriteria decision-making procedure. The effectiveness of the proposed control strategy has been verified with reference to a highway bridge and to two specific worldwide seismic regions.

  20. Evidence for fast seismic lid structure beneath the Californian margin and its implication on regional plate deformation

    Science.gov (United States)

    Lai, V. H.; Graves, R. W.; Wei, S.; Helmberger, D. V.

    2015-12-01

    The lithospheric structure of the Pacific and North American plates play an important role in modulating plate deformation along the California margin. Pure path models indicate that the Pacific plate has a fast thick (80km) lid overlaying a strong low velocity zone (LVZ) extending to beyond 300 km depth. In contrast, the North America structure is characterized by a relatively thin (25-35km) lid and a shallow LVZ. Vertical ray paths have similar travel times across the plate boundary for the two models, making resolution of the transitional structure difficult. Earthquakes such as the 2014 March 10 Mw 6.8 Mendocino and 2014 August 25 Mw 6.0 Napa events recorded at regional distances across California provide an opportunity to study horizontal paths and track the lateral variation in the lower crust-uppermost mantle structure under the Californian margin. Observations from both Napa and Mendocino events show direct SH-wave arrivals at Southern California Seismic Network (SCSN) stations are systematically earlier (up to 10 s) for coastal and island stations relative to inland sites. The shift in SH arrival times may be due to features such as varying crustal thickness, varying upper mantle velocity and the presence of a fast seismic lid. To test the different hypotheses, we perform extensive forward modeling using both 1-D frequency-wavenumber and 3-D finite-difference approaches. The model that best fits the SH arrival times has a fast lid (Vs = 4.7 km/s) underlying the whole California margin, with the lid increasing in thickness from east to west to a maximum thickness about 70 km in the western offshore region. The fast, thick seismic lid lends strength and rigidity to the Pacific plate lithosphere in contrast with the weaker North American continental plate, which influences the overall plate deformation along the Californian margin and is in agreement with GPS measurements.

  1. Seismic hazard assessment over time: Modelling earthquakes in Taiwan

    Science.gov (United States)

    Chan, Chung-Han; Wang, Yu; Wang, Yu-Ju; Lee, Ya-Ting

    2017-04-01

    To assess the seismic hazard with temporal change in Taiwan, we develop a new approach, combining both the Brownian Passage Time (BPT) model and the Coulomb stress change, and implement the seismogenic source parameters by the Taiwan Earthquake Model (TEM). The BPT model was adopted to describe the rupture recurrence intervals of the specific fault sources, together with the time elapsed since the last fault-rupture to derive their long-term rupture probability. We also evaluate the short-term seismicity rate change based on the static Coulomb stress interaction between seismogenic sources. By considering above time-dependent factors, our new combined model suggests an increased long-term seismic hazard in the vicinity of active faults along the western Coastal Plain and the Longitudinal Valley, where active faults have short recurrence intervals and long elapsed time since their last ruptures, and/or short-term elevated hazard levels right after the occurrence of large earthquakes due to the stress triggering effect. The stress enhanced by the February 6th, 2016, Meinong ML 6.6 earthquake also significantly increased rupture probabilities of several neighbouring seismogenic sources in Southwestern Taiwan and raised hazard level in the near future. Our approach draws on the advantage of incorporating long- and short-term models, to provide time-dependent earthquake probability constraints. Our time-dependent model considers more detailed information than any other published models. It thus offers decision-makers and public officials an adequate basis for rapid evaluations of and response to future emergency scenarios such as victim relocation and sheltering.

  2. Study of seismicity in the NW Himalaya and adjoining regions using IMS network

    Science.gov (United States)

    Ali, Sherif M.; Shanker, D.

    2017-03-01

    The Reviewed Event Bulletin (REB) of the International Data Center (IDC) has been used in order to investigate the seismicity of the Northwest Himalaya and its neighboring region for the time period June 1999 to March 2015 within the geographical coordinates 25-40° N latitude and 65-85° E longitude. We have used a very precisely located earthquake dataset recorded by the International Monitoring System (IMS) Network containing 7,583 events with body wave magnitudes from 2.5 to 6.3. The study area has been subdivided into six regions based on the Flinn-Engdahl (F-E) seismic and geographical regionalization scheme, which was used as the region classifications of the International Data Center catalog. The examined region includes NW India, Pakistan, Nepal, Xizang, Kashmir, and Hindukush. For each region, Magnitudes of completeness (Mc) and Gutenberg-Richter (GR) recurrence parameters ( a and b values) have been estimated. The Gutenberg-Richter analysis is preceded by an overview of the seismotectonics of the study area. The obtained Mc values vary from 3.5 to 3.9. The lower value of Mc was found mainly in Xizang region whereas the higher Mc threshold is evident in Pakistan region. However, the b values vary from 1.19 to 1.48. The lowest b value is recorded in Xizang region, which is mostly related to the Main Karakoram Thrust (MKT) fault, whereas the highest b values are recorded in NW India and Kashmir regions, which are mostly related to the Main Frontal Thrust (MFT) fault. The REB for the selected period has been compared to the most renowned bulletin of global seismicity, namely that issued by the National Earthquake Information Center (NEIC) of the United States Geological Survey (USGS). A study of 4,821 events recorded by USGS in the study region indicates that about 36 % of seismic events were missed and the catalog is considered as complete for events with magnitudes ≥4.0. However, both a and b values are obviously higher than those of IMS catalog. The a

  3. Study of seismicity in the NW Himalaya and adjoining regions using IMS network

    Science.gov (United States)

    Ali, Sherif M.; Shanker, D.

    2016-08-01

    The Reviewed Event Bulletin (REB) of the International Data Center (IDC) has been used in order to investigate the seismicity of the Northwest Himalaya and its neighboring region for the time period June 1999 to March 2015 within the geographical coordinates 25-40° N latitude and 65-85° E longitude. We have used a very precisely located earthquake dataset recorded by the International Monitoring System (IMS) Network containing 7,583 events with body wave magnitudes from 2.5 to 6.3. The study area has been subdivided into six regions based on the Flinn-Engdahl (F-E) seismic and geographical regionalization scheme, which was used as the region classifications of the International Data Center catalog. The examined region includes NW India, Pakistan, Nepal, Xizang, Kashmir, and Hindukush. For each region, Magnitudes of completeness (Mc) and Gutenberg-Richter (GR) recurrence parameters (a and b values) have been estimated. The Gutenberg-Richter analysis is preceded by an overview of the seismotectonics of the study area. The obtained Mc values vary from 3.5 to 3.9. The lower value of Mc was found mainly in Xizang region whereas the higher Mc threshold is evident in Pakistan region. However, the b values vary from 1.19 to 1.48. The lowest b value is recorded in Xizang region, which is mostly related to the Main Karakoram Thrust (MKT) fault, whereas the highest b values are recorded in NW India and Kashmir regions, which are mostly related to the Main Frontal Thrust (MFT) fault. The REB for the selected period has been compared to the most renowned bulletin of global seismicity, namely that issued by the National Earthquake Information Center (NEIC) of the United States Geological Survey (USGS). A study of 4,821 events recorded by USGS in the study region indicates that about 36 % of seismic events were missed and the catalog is considered as complete for events with magnitudes ≥4.0. However, both a and b values are obviously higher than those of IMS catalog. The a

  4. Multidimensional analysis and probabilistic model of volcanic and seismic activities

    Science.gov (United States)

    Fedorov, V.

    2009-04-01

    .I. Gushchenko, 1979) and seismological (database of USGS/NEIC Significant Worldwide Earthquakes, 2150 B.C.- 1994 A.D.) information which displays dynamics of endogenic relief-forming processes over a period of 1900 to 1994. In the course of the analysis, a substitution of calendar variable by a corresponding astronomical one has been performed and the epoch superposition method was applied. In essence, the method consists in that the massifs of information on volcanic eruptions (over a period of 1900 to 1977) and seismic events (1900-1994) are differentiated with respect to value of astronomical parameters which correspond to the calendar dates of the known eruptions and earthquakes, regardless of the calendar year. The obtained spectra of volcanic eruptions and violent earthquake distribution in the fields of the Earth orbital movement parameters were used as a basis for calculation of frequency spectra and diurnal probability of volcanic and seismic activity. The objective of the proposed investigations is a probabilistic model development of the volcanic and seismic events, as well as GIS designing for monitoring and forecast of volcanic and seismic activities. In accordance with the stated objective, three probability parameters have been found in the course of preliminary studies; they form the basis for GIS-monitoring and forecast development. 1. A multidimensional analysis of volcanic eruption and earthquakes (of magnitude 7) have been performed in terms of the Earth orbital movement. Probability characteristics of volcanism and seismicity have been defined for the Earth as a whole. Time intervals have been identified with a diurnal probability twice as great as the mean value. Diurnal probability of volcanic and seismic events has been calculated up to 2020. 2. A regularity is found in duration of dormant (repose) periods has been established. A relationship has been found between the distribution of the repose period probability density and duration of the period. 3

  5. Preliminary Interpretations of Multi-Channel Seismic Reflection and Magnetic Data on North Anatolian Fault (NAF) in the Eastern Marmara Region, Turkey

    Science.gov (United States)

    Gözde Okut Toksoy, Nigar; Kurt, Hülya; İşseven, Turgay

    2017-04-01

    The North Anatolian Fault (NAF) is 1600 km long, right lateral strike-slip fault nearly E-W elongated between Karlıova in the east and Saros Gulf in the west. NAF splays into two major strands near the west of Bolu city as Northern and Southern strands. Northern strand passes Sapanca Lake and extends towards west and reaches Marmara Sea through the Gulf of Izmit. The area has high seismicity; 1999 Kocaeli (Mw=7.4) and 1999 Düzce (Mw=7.2) earthquakes caused approximately 150 km long surface rupture between the Gulf of Izmit and Bolu. The rupture has four distinct fault segments as Gölcük, Sapanca, Sakarya, and Karadere from west to east. In this study multi-channel seismic and magnetic data are collected for the first time on the Sapanca Segment to investigate the surficial and deeper geometry of the NAF. Previously, the NAF in the eastern Marmara region is investigated using by paleo-seismological data from trenches on the surface rupture of fault or the geomorphological data (Lettis et al., 2000; Dikbaş and Akyüz, 2010) which have shallower depth targets. Crustal structure and seismic velocities for Central Anatolia and eastern Marmara regions are obtained from deeper targeted refraction data (Gürbüz et al., 1992). However, their velocity models do not have the spatial resolution to determine details of the fault zone structure. Multi-channel seismic and magnetic data in this study were acquired on two N-S directed profiles crossing NAF perpendicularly near Kartepe on the western part of the Sapanca Lake in October 2016. The receiver interval is 5 m, shot interval is 5-10 m, and the total length of the profiles are approximately 1400 m. Buffalo Gun is used as a seismic source for deeper penetration. Conventional seismic reflection processing steps are applied to the data. These are geometry definition, editing, filtering, static correction, velocity analysis and deconvolution, stacking and migration. Echos seismic software package in Geophysical Department

  6. On the Imminent Regional Seismic Activity Forecasting Using INTERMAGNET and Sun-Moon Tide Code Data

    CERN Document Server

    Mavrodiev, Strachimir Cht; Kikuashvili, Giorgi; Botev, Emil; Getsov, Petar; Mardirossian, Garo; Sotirov, Georgi; Teodossiev, Dimitar

    2016-01-01

    In this paper we present an approach for forecasting the imminent regional seismic activity by using geomagnetic data and Earth tide data. The time periods of seismic activity are the time periods around the Sun-Moon extreme of the diurnal average value of the tide vector module. For analyzing the geomagnetic data behaviour we use diurnal standard deviation of geomagnetic vector components F for calculating the time variance Geomag Signal. The Sun storm influence is avoided by using data for daily A-indexes (published by NOAA). The precursor signal for forecasting the incoming regional seismic activity is a simple function of the present and previous day Geomag Signal and A-indexes values. The reliability of the geomagnetic when, regional precursor is demonstrated by using statistical analysis of day difference between the times of predicted and occurred earthquakes. The base of the analysis is a natural hypothesis that the predicted earthquake is the one whose surface energy density in the monitoring point i...

  7. A modified symplectic PRK scheme for seismic wave modeling

    Science.gov (United States)

    Liu, Shaolin; Yang, Dinghui; Ma, Jian

    2017-02-01

    A new scheme for the temporal discretization of the seismic wave equation is constructed based on symplectic geometric theory and a modified strategy. The ordinary differential equation in terms of time, which is obtained after spatial discretization via the spectral-element method, is transformed into a Hamiltonian system. A symplectic partitioned Runge-Kutta (PRK) scheme is used to solve the Hamiltonian system. A term related to the multiplication of the spatial discretization operator with the seismic wave velocity vector is added into the symplectic PRK scheme to create a modified symplectic PRK scheme. The symplectic coefficients of the new scheme are determined via Taylor series expansion. The positive coefficients of the scheme indicate that its long-term computational capability is more powerful than that of conventional symplectic schemes. An exhaustive theoretical analysis reveals that the new scheme is highly stable and has low numerical dispersion. The results of three numerical experiments demonstrate the high efficiency of this method for seismic wave modeling.

  8. Understanding Space Weather influence on earthquake triggering to shield people living in seismic regions

    Science.gov (United States)

    Khachikyan, Galina; Inchin, Alexander; Kim, Alexander; Khassanov, Eldar

    2016-07-01

    There is an idea at present that space weather can influence not only the technological infrastructure and people's health, but seismic activity as well. Space weather impact on the Earth results from magnetic reconnection between the Sun's and Earth's magnetic fields. The effectiveness of reconnection depends on sign and magnitude of Z-components in solar wind magnetic field and earth's magnetic field as measured in the geocentric solar magnetosphere (GSM) coordinate system. The more negative value of Zgsm in the solar wind magnetic field, and the more positive value of Zgsm in the geomagnetic field, the more solar wind energy penetrates into the earth's environment due to reconnection. It was found recently by Khachikyan et al. [2012, http://www.scirp.org/journal/ijg] that maximal possible earthquake magnitude in a particular seismic region (seismic potential - Mmax) may be determined, in first approximation, on the base of maximal geomagnetic Zgsm value in this region, namely: Mmax = (5.22 +- 0.17) + (0.78 +- 0.06) x [abs (Zgsm)]. In this report we present statistical results on association between variations in space weather and global seismic activity, and demonstrate that a great Sumatra earthquake (M=9.1, on December 26, 2004, at 00:58:53 GMT) indeed occurred in region where the geomagnetic Zgsm components are largest at the globe. In the time of earthquake occurrence, geomagnetic Zgsm value in the epicenter (3.30N, 95.980E) was equal to ~37147 nT. A range of possible maximal magnitude, as estimated from above relation, could be of 8.8 - 9.2. The recorded magnitude M=9.1 is within this range.

  9. A smoothed stochastic earthquake rate model considering seismicity and fault moment release for Europe

    Science.gov (United States)

    Hiemer, S.; Woessner, J.; Basili, R.; Danciu, L.; Giardini, D.; Wiemer, S.

    2014-08-01

    We present a time-independent gridded earthquake rate forecast for the European region including Turkey. The spatial component of our model is based on kernel density estimation techniques, which we applied to both past earthquake locations and fault moment release on mapped crustal faults and subduction zone interfaces with assigned slip rates. Our forecast relies on the assumption that the locations of past seismicity is a good guide to future seismicity, and that future large-magnitude events occur more likely in the vicinity of known faults. We show that the optimal weighted sum of the corresponding two spatial densities depends on the magnitude range considered. The kernel bandwidths and density weighting function are optimized using retrospective likelihood-based forecast experiments. We computed earthquake activity rates (a- and b-value) of the truncated Gutenberg-Richter distribution separately for crustal and subduction seismicity based on a maximum likelihood approach that considers the spatial and temporal completeness history of the catalogue. The final annual rate of our forecast is purely driven by the maximum likelihood fit of activity rates to the catalogue data, whereas its spatial component incorporates contributions from both earthquake and fault moment-rate densities. Our model constitutes one branch of the earthquake source model logic tree of the 2013 European seismic hazard model released by the EU-FP7 project `Seismic HAzard haRmonization in Europe' (SHARE) and contributes to the assessment of epistemic uncertainties in earthquake activity rates. We performed retrospective and pseudo-prospective likelihood consistency tests to underline the reliability of our model and SHARE's area source model (ASM) using the testing algorithms applied in the collaboratory for the study of earthquake predictability (CSEP). We comparatively tested our model's forecasting skill against the ASM and find a statistically significant better performance for

  10. Physical Accuracy of Q Models of Seismic Attenuation

    Science.gov (United States)

    Morozov, I. B.

    2016-12-01

    Accuracy of theoretical models is a required prerequisite for any type of seismic imaging and interpretation. Among all geophysical disciplines, the theory of seismic and tidal attenuation is the least developed, and most practical studies use viscoelastic models based on empirical Q factors. To simplify imaging and inversions, the Qs are often approximated as frequency-independent or following a power law with frequency. However, simplicity of inversion should not outweigh the problematic physical accuracy of such models. Typical images of spatially-variable crustal and mantle Qs are "apparent," analogously to pseudo-depth, apparent-resistivity images in electrical imaging. Problems with Q models can be seen from controversial general observations present in many studies; for example: 1) In global Q models, bulk attenuation is much lower than the shear one throughout the whole Earth. This is considered a fundamental relation for the Earth; nevertheless, it is also very peculiar physically and suggests a negative Q for the Lamé modulus. This relation is also not supported by most first-principle models of materials and laboratory studies. 2) The Q parameterization requires that the entire outer core of the Earth is assigned zero attenuation, despite its large volume, presence of viscosity and shear deformation in free oscillations. 3) In laboratory and surface-wave studies, the bulk and shear Qs can be different for different wave modes, different sample sizes boundary conditions on the surface. Similarly, the Qs measured from body-S, Love, Lg, or ScS waves may not equal each other. 4) In seismic coda studies, the Q is often found to be linearly (or even faster) increasing with frequency. Such character of energy dissipation is controversial physically, but can be readily explained as an artifact of inaccurately-known geometrical spreading. To overcome the physical inaccuracies and apparent character of seismic attenuation models, mechanical theories of materials

  11. Variation of Seismic Coda Wave Attenuation in the Garhwal Region, Northwestern Himalaya

    Science.gov (United States)

    Tripathi, Jayant N.; Singh, Priyamvada; Sharma, Mukat L.

    2012-01-01

    Seismic coda wave attenuation ( Q_{text{c}}^{ - 1} ) characteristics in the Garhwal region, northwestern Himalaya is studied using 113 short-period, vertical component seismic observations from local events with hypocentral distance less than 250 km and magnitude range between 1.0 to 4.0. They are located mainly in the vicinity of the Main Boundary Thrust (MBT) and the Main Central Thrust (MCT), which are well-defined tectonic discontinuities in the Himalayas. Coda wave attenuation ( Q_{text{c}}^{ - 1} ) is estimated using the single isotropic scattering method at central frequencies 1.5, 3, 5, 7, 9, 12, 16, 20, 24 and 28 Hz using several starting lapse times and coda window lengths for the analysis. Results show that the ( Q_{text{c}}^{ - 1} ) values are frequency dependent in the considered frequency range, and they fit the frequency power law ( Q_{text{c}}^{ - 1} left( f right) = Q0^{ - 1} f^{ - n} ). The Q 0 ( Q c at 1 Hz) estimates vary from about 50 for a 10 s lapse time and 10 s window length, to about 350 for a 60 s lapse time and 60 s window length combination. The exponent of the frequency dependence law, n ranges from 1.2 to 0.7; however, it is greater than 0.8, in general, which correlates well with the values obtained in other seismically and tectonically active and highly heterogeneous regions. The attenuation in the Garhwal region is found to be lower than the Q {c/-1} values obtained for other seismically active regions of the world; however, it is comparable to other regions of India. The spatial variation of coda attenuation indicates that the level of heterogeneity decreases with increasing depth. The variation of coda attenuation has been estimated for different lapse time and window length combinations to observe the effect with depth and it indicates that the upper lithosphere is more active seismically as compared to the lower lithosphere and the heterogeneity decreases with increasing depth.

  12. A seismic design of nuclear reactor building structures applying seismic isolation system in a seismicity region-a feasibility case study in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Kubo, Tetsuo [The University of Tokyo, Tokyo (Japan); Yamamoto, Tomofumi; Sato, Kunihiko [Mitsubishi Heavy Industries, Ltd., Kobe (Japan); Jimbo, Masakazu [Toshiba Corporation, Yokohama (Japan); Imaoka, Tetsuo [Hitachi-GE Nuclear Energy, Ltd., Hitachi (Japan); Umeki, Yoshito [Chubu Electric Power Co. Inc., Nagoya (Japan)

    2014-10-15

    A feasibility study on the seismic design of nuclear reactor buildings with application of a seismic isolation system is introduced. After the Hyogo-ken Nanbu earthquake in Japan of 1995, seismic isolation technologies have been widely employed for commercial buildings. Having become a mature technology, seismic isolation systems can be applied to NPP facilities in areas of high seismicity. Two reactor buildings are discussed, representing the PWR and BWR buildings in Japan, and the application of seismic isolation systems is discussed. The isolation system employing rubber bearings with a lead plug positioned (LRB) is examined. Through a series of seismic response analyses using the so-named standard design earthquake motions covering the design basis earthquake motions obtained for NPP sites in Japan, the responses of the seismic isolated reactor buildings are evaluated. It is revealed that for the building structures examined herein: (1) the responses of both isolated buildings and isolating LRBs fulfill the specified design criteria; (2) the responses obtained for the isolating LRBs first reach the ultimate condition when intensity of motion is 2.0 to 2.5 times as large as that of the design-basis; and (3) the responses of isolated reactor building fall below the range of the prescribed criteria.

  13. Region-specific deterministic and probabilistic seismic hazard analysis of Kanpur city

    Indian Academy of Sciences (India)

    Anbazhagan P; Ketan Bajaj; Nairwita Dutta; Sayed S R Moustafa; Nassir S N Al-Arifi

    2017-02-01

    A seismic hazard map of Kanpur city has been developed considering the region-specific seismotectonic parameters within a 500-km radius by deterministic and probabilistic approaches. The maximum probable earthquake magnitude \\textit(Mmax) for each seismic source has been estimated by considering the regional rupture characteristics method and has been compared with the maximum magnitude observed \\textit(Mobsmax), \\textit(Mobsmax) + 0.5 and Kijko method. The best suitable ground motion prediction equations (GMPE) were selected from 27 applicable GMPEs based on the ‘efficacy test’. Furthermore, different weight factors were assigned to different Mmax values and the selected GMPE to calculate the final hazard value. Peak ground acceleration and spectral acceleration at 0.2 and 1 s were estimated and mapped for worstcase scenario and 2 and 10% probability of exceedance for 50 years. Peak ground acceleration (PGA) showed a variation from 0.04 to 0.36 g for DSHA, from 0.02 to 0.32 g and 0.092 to 0.1525 g for 2 and 10% probability in 50 years, respectively. A normalised site-specific design spectrum has been developed considering three vulnerable sources based on deaggregation at the city center and the results are compared with the recent 2011 Sikkim and 2015 Nepal earthquakes, and the Indian seismic code IS 1893.

  14. Time-dependent Induced Seismicity Rates Described with an Epidemic Type Aftershock Sequence Model at The Geysers Geothermal Field, California

    Science.gov (United States)

    Johnson, C. W.; Totten, E. J.; Burgmann, R.

    2015-12-01

    To improve understanding of the link between injection/production activity and seismicity, we apply an Epidemic Type Aftershock Sequence (ETAS) model to an earthquake catalog from The Geysers geothermal field (GGF) between 2005-2015 using >140,000 events and Mc 0.8 . We partition the catalog along a northeast-southwest trending divide, which corresponds to regions of high and low levels of enhanced geothermal stimulation (EGS) across the field. The ETAS model is fit to the seismicity data using a 6-month sliding window with a 1-month time step to determine the background seismicity rate. We generate monthly time series of the time-dependent background seismicity rate in 1-km depth intervals from 0-5km. The average wellhead depth is 2-3 km and the background seismicity rates above this depth do not correlate well with field-wide injected masses over the time period of interest. The auto correlation results show a 12-month period for monthly time series proximal to the average wellhead depths (2-3km and 3-4km) for northwest GGF strongly correlates with field-wide fluid injection masses, with a four-month phase shift between the two depth intervals as fluid migrates deeper. This periodicity is not observed for the deeper depth interval of 4-5 km, where monthly background seismicity rates reduce to near zero. Cross-correlation analysis using the monthly time series for background seismicity rate and the field-wide injection, production and net injection (injection minus production) suggest that injection most directly modulates seismicity. Periodicity in the background seismicity is not observed as strongly in the time series for the southeast field. We suggest that the variation in background seismicity rate is a proxy for pore-pressure diffusion of injected fluids at depth. We deduce that the contrast between the background seismicity rates in the northwest and southeast GGF is a result of reduced EGS activity in the southeast region.

  15. A seismic reflection and GLORIA study of compressional deformation in the Gorringe Bank region, eastern North Atlantic

    Science.gov (United States)

    Hayward, N.; Watts, A. B.; Westbrook, G. K.; Collier, J. S.

    1999-09-01

    Seismic reflection and GLORIA side-scan sonar data obtained on RRS Charles Darwin cruise CD64 reveal new information on the styles of deformation in the Gorringe Bank region, at the eastern end of the Azores-Gibraltar plate boundary. Previous studies suggest that Gorringe Bank was formed by the overthrusting of a portion of the African plate upon the Eurasian plate. The new seismic data show, however, that the most intensely deformed region is located south of Gorringe Bank, on the northern flanks of a NW-SE-trending submarine ridge which includes the Ampere and Coral Patch seamounts. The deformation is expressed as long-wavelength (up to 60 km), large-amplitude (up to 800 m) folds in the sediments and underlying acoustic basement, which in places are associated with one or more reverse faults, and as a fabric of short-wavelength folds (up to 3 km) with a NE trend. In contrast, the same sedimentary units when traced beneath the flanking plains are undeformed, except for some faults with a small throw (~30 m), some of which offset the seafloor. GLORIA data show that recent deformation is broadly distributed over the region. Structural trends rotate from 45 deg in the west to 70 deg in the east of the region, nearly perpendicular to the NW-verging plate motion vectors as determined from plate kinematic models. Flexure modelling suggests that a portion of Gorringe Bank has loaded 152 Ma oceanic lithosphere and that a maximum of 50 km of shortening has occurred at Gorringe Bank since the mid-Miocene. Our observations support a model in which there is no single plate boundary in the region, rather that the deformation is distributed over a 200-330 km wide zone.

  16. Forward modeling to improve seismic reflection energy of a protective coal seam based on Zoeppritz equation

    Institute of Scientific and Technical Information of China (English)

    TAO Wen-peng; DONG Shou-hua; LI Yang

    2008-01-01

    In seismic exploration for coal, seismic waves are very difficult to transmit downward because of high velocity protec-tive layers, making the reflection information very hard to receive above ground. Based on the Snell law and the Zoeppritz equation, we studied the relationship between the incidence angle and reflection seismic wave energy using a forward model of level media. The result shows that the seismic wave energy has a sudden increase at the critical angle. Based on the energy propagation rule, using big offset to receive the seismic wave energy under a protective layer can effectively reduce its protection effect.

  17. A model for seismicity rates observed during the 1982-1984 unrest at Campi Flegrei caldera (Italy)

    Science.gov (United States)

    Belardinelli, M. E.; Bizzarri, A.; Berrino, G.; Ricciardi, G. P.

    2011-02-01

    We consider the space-time distribution of seismicity during the 1982-1984 unrest at Campi Flegrei caldera (Italy) where a correlation between seismicity and rate of ground uplift was suggested. In order to investigate this effect, we present a model based on stress transfer from the deformation source responsible for the unrest to potential faults. We compute static stress changes caused by an inflating source in a layered half-space. Stress changes are evaluated on optimally oriented planes for shear failure, assuming a regional stress with horizontal extensional axis trending NNE-SSW. The inflating source is modeled as inferred by previous studies from inversion of geodetic data with the same crustal model here assumed. The magnitude of the regional stress is constrained by imposing an initial condition of "close to failure" to potential faults. The resulting spatial distribution of stress changes is in agreement with observations. We assume that the temporal evolution of ground displacement, observed by a tide-gauge at Pozzuoli, was due mainly to time dependent processes occurring at the inflating source. We approximate this time dependence in piecewise-linear way and we attribute it to each component of average stress-change in the region interested by the observed seismicity. Then we evaluate the effect of a time dependent stressing rate on seismicity, by following the approach indicated by Dieterich (1994) on the basis of the rate- and state-dependent rheology of faults. The seismicity rate history resulting from our model is in general agreement with data during the period 1982-1984 for reasonable values of unconstrained model-parameters, the initial value of the direct effect of friction and the reference shear stressing rate. In particular, this application shows that a decreasing stressing-rate is effective in damping the seismicity rate.

  18. Seismicity pattern: an indicator of source region of volcanism at convergent plate margins

    Science.gov (United States)

    Špičák, Aleš; Hanuš, Václav; Vaněk, Jiří

    2004-04-01

    The results of detailed investigation into the geometry of distribution of earthquakes around and below the volcanoes Korovin, Cleveland, Makushin, Yake-Dake, Oshima, Lewotobi, Fuego, Sangay, Nisyros and Montagne Pelée at convergent plate margins are presented. The ISC hypocentral determinations for the period 1964-1999, based on data of global seismic network and relocated by Engdahl, van der Hilst and Buland, have been used. The aim of this study has been to contribute to the solution of the problem of location of source regions of primary magma for calc-alkaline volcanoes spatially and genetically related to the process of subduction. Several specific features of seismicity pattern were revealed in this context. (i) A clear occurrence of the intermediate-depth aseismic gap (IDAG) in the Wadati-Benioff zone (WBZ) below all investigated active volcanoes. We interpret this part of the subducted slab, which does not contain any teleseismically recorded earthquake with magnitude greater than 4.0, as a partially melted domain of oceanic lithosphere and as a possible source of primary magma for calc-alkaline volcanoes. (ii) A set of earthquakes in the shape of a seismically active column (SAC) seems to exists in the continental wedge below volcanoes Korovin, Makushin and Sangay. The seismically active columns probably reach from the Earth surface down to the aseismic gap in the Wadati-Benioff zone. This points to the possibility that the upper mantle overlying the subducted slab does not contain large melted domains, displays an intense fracturing and is not likely to represent the site of magma generation. (iii) In the continental wedge below the volcanoes Cleveland, Fuego, Nisyros, Yake-Dake, Oshima and Lewotobi, shallow seismicity occurs down to the depth of 50 km. The domain without any earthquakes between the shallow seismically active column and the aseismic gap in the Wadati-Benioff zone in the depth range of 50-100 km does not exclude the melting of the mantle

  19. Seismic Sedimentology Interpretation Method of Meandering Fluvial Reservoir:From Model to Real Data

    Institute of Scientific and Technical Information of China (English)

    Tao Zhang; Xianguo Zhang; Chengyan Lin; Jingfeng Yu; Shouxiu Zhang

    2015-01-01

    Reservoir architecture of meandering river deposition is complex and traditional seismic facies interpretation method cannot characterize it when layer thickness is under seismic vertical reso-lution. In this study, a seismic sedimentology interpretation method and workflow for point bar char-acterization is built. Firstly, the influences of seismic frequency and sandstone thickness on seismic re-flection are analyzed by outcrop detection with ground penetrating radar (GPR) and seismic forward modeling. It is found that (1) sandstone thickness can influence seismic reflection of point bar architec-ture. With the increasing of sandstone thickness from 1/4 wavelength (λ) to λ/2, seismic reflection ge-ometries various from ambiguous reflection,“V”type reflection to“X”type reflection;(2) seismic fre-quency can influence reservoirs’ seismic reflection geometry. Seismic events follow inclined lateral ag-gradation surfaces, which is isochronic depositional boundaries, in high frequency seismic data while the events extend along lithologic surfaces, which are level, in low frequency data. Secondly, strata slice interpretation method for thin layer depositional characterization is discussed with seismic forward modeling. Lastly, a method and workflow based on the above study is built which includes seismic fre-quency analysis, 90º phasing, stratal slicing and integrated interpretation of slice and seismic profile. This method is used in real data study in Tiger shoal, the Gulf of Mexico. Two episodes of meandering fluvial deposition is recognized in the study layer. Sandstone of the lower unit, which is formed in low base level stage, distributes limited. Sandstone distribution dimension and channel sinuosity become larger in the upper layer, which is high base level deposition.

  20. Seismic base isolation: Elastomer characterization, bearing modeling and system response

    Energy Technology Data Exchange (ETDEWEB)

    Kulak, R.F.; Wang, C.Y.; Hughes, T.H.

    1991-01-01

    This paper discusses several major aspects of seismic base isolation systems that employ laminated elastomer bearings. Elastomer constitutive models currently being used to represent the nonlinear elastic and hysteretic behavior are discussed. Some aspects of mechanical characterization testing of elastomers is presented along with representative tests results. The development of a finite element based mesh generator for laminated elastomer bearings is presented. Recent advances in the simulation of base isolated structures to earthquake motions are presented along with a sample problem. 13 refs., 19 figs., 1 tab.

  1. The seismic cycle at subduction thrusts: 2. Dynamic implications of geodynamic simulations validated with laboratory models

    KAUST Repository

    van Dinther, Y.

    2013-04-01

    The physics governing the seismic cycle at seismically active subduction zones remains poorly understood due to restricted direct observations in time and space. To investigate subduction zone dynamics and associated interplate seismicity, we validate a continuum, visco-elasto-plastic numerical model with a new laboratory approach (Paper 1). The analogous laboratory setup includes a visco-elastic gelatin wedge underthrusted by a rigid plate with defined velocity-weakening and -strengthening regions. Our geodynamic simulation approach includes velocity-weakening friction to spontaneously generate a series of fast frictional instabilities that correspond to analog earthquakes. A match between numerical and laboratory source parameters is obtained when velocity-strengthening is applied in the aseismic regions to stabilize the rupture. Spontaneous evolution of absolute stresses leads to nucleation by coalescence of neighboring patches, mainly occurring at evolving asperities near the seismogenic zone limits. Consequently, a crack-, or occasionally even pulse-like, rupture propagates toward the opposite side of the seismogenic zone by increasing stresses ahead of its rupture front, until it arrests on a barrier. The resulting surface displacements qualitatively agree with geodetic observations and show landward and, from near the downdip limit, upward interseismic motions. These are rebound and reversed coseismically. This slip increases adjacent stresses, which are relaxed postseismically by afterslip and thereby produce persistent seaward motions. The wide range of observed physical phenomena, including back-propagation and repeated slip, and the agreement with laboratory results demonstrate that visco-elasto-plastic geodynamic models with rate-dependent friction form a new tool that can greatly contribute to our understanding of the seismic cycle at subduction zones.

  2. Grid-Search Location Methods for Ground-Truth Collection From Local and Regional Seismic Networks

    Energy Technology Data Exchange (ETDEWEB)

    William Rodi; Craig A. Schultz; Gardar Johannesson; Stephen C. Myers

    2005-05-13

    This project investigated new techniques for improving seismic event locations derived from regional and local networks. The technqiues include a new approach to empirical travel-time calibration that simultaneously fits data from multiple stations and events, using a generalization of the kriging method, and predicts travel-time corrections for arbitrary event-station paths. We combined this calibration approach with grid-search event location to produce a prototype new multiple-event location method that allows the use of spatially well-distributed events and takes into account correlations between the travel-time corrections from proximate event-station paths. Preliminary tests with a high quality data set from Nevada Test Site explosions indicated that our new calibration/location method offers improvement over the conventional multiple-event location methods now in common use, and is applicable to more general event-station geometries than the conventional methods. The tests were limited, however, and further research is needed to fully evaluate, and improve, the approach. Our project also demonstrated the importance of using a realistic model for observational errors in an event location procedure. We took the initial steps in developing a new error model based on mixture-of-Gaussians probability distributions, which possess the properties necessary to characterize the complex arrival time error processes that can occur when picking low signal-to-noise arrivals. We investigated various inference methods for fitting these distributions to observed travel-time residuals, including a Markov Chain Monte Carlo technique for computing Bayesian estimates of the distribution parameters.

  3. A Kirchhoff approach to seismic modeling and prestack depth migration

    Science.gov (United States)

    Liu, Zhen-Yue

    1993-05-01

    The Kirchhoff integral provides a robust method for implementing seismic modeling and prestack depth migration, which can handle lateral velocity variation and turning waves. With a little extra computation cost, the Kirchoff-type migration can obtain multiple outputs that have the same phase but different amplitudes, compared with that of other migration methods. The ratio of these amplitudes is helpful in computing some quantities such as reflection angle. I develop a seismic modeling and prestack depth migration method based on the Kirchhoff integral, that handles both laterally variant velocity and a dip beyond 90 degrees. The method uses a finite-difference algorithm to calculate travel times and WKBJ amplitudes for the Kirchhoff integral. Compared to ray-tracing algorithms, the finite-difference algorithm gives an efficient implementation and single-valued quantities (first arrivals) on output. In my finite difference algorithm, the upwind scheme is used to calculate travel times, and the Crank-Nicolson scheme is used to calculate amplitudes. Moreover, interpolation is applied to save computation cost. The modeling and migration algorithms require a smooth velocity function. I develop a velocity-smoothing technique based on damped least-squares to aid in obtaining a successful migration.

  4. Towards a Multi-Resolution Model of Seismic Risk in Central Asia. Challenge and perspectives

    Science.gov (United States)

    Pittore, M.; Wieland, M.; Bindi, D.; Parolai, S.

    2011-12-01

    Assessing seismic risk, defined as the probability of occurrence of economical and social losses as consequence of an earthquake, both at regional and at local scale is a challenging, multi-disciplinary task. In order to provide a reliable estimate, diverse information must be gathered by seismologists, geologists, engineers and civil authorities, and carefully integrated keeping into account the different levels of uncertainty. The research towards an integrated methodology, able to seamlessly describe seismic risk at different spatial scales is challenging, but discloses new application perspectives, particularly in those countries which suffer from a relevant seismic hazard but do not have resources for a standard assessment. Central Asian countries in particular, which exhibit one of the highest seismic hazard in the world, are experiencing a steady demographic growth, often accompanied by informal settlement and urban sprawling. A reliable evaluation of how these factors affect the seismic risk, together with a realistic assessment of the assets exposed to seismic hazard and their structural vulnerability is of particular importance, in order to undertake proper mitigation actions and to promptly and efficiently react to a catastrophic event. New strategies are needed to efficiently cope with systematic lack of information and uncertainties. An original approach is presented to assess seismic risk based on integration of information coming from remote-sensing and ground-based panoramic imaging, in situ measurements, expert knowledge and already available data. Efficient sampling strategies based on freely available medium-resolution multi-spectral satellite images are adopted to optimize data collection and validation, in a multi-scale approach. Panoramic imaging is also considered as a valuable ground-based visual data collection technique, suitable both for manual and automatic analysis. A full-probabilistic framework based on Bayes Network is proposed to

  5. Improved cavity detection from coupled seismic and hydrologic models

    Science.gov (United States)

    Desilets, S.; Bonal, N. D.; Desilets, D.

    2012-12-01

    Seismic methods hold much promise for cavity detection, but the results from field measurements have been frustratingly inconsistent between field sites. The reasons for the inconsistencies are not fully understood, though water saturation in the near-surface may be responsible to some extent. The conventional approach has been to focus on reflections and refractions generated from the impedance contrast of the cavity wall itself, where the dimensions and geometry of the cavity should play key roles. Here, we instead focus on the influence of impedance contrasts that are generated by hydrologic processes in the adjacent porous medium. These contrasts can potentially increase or decrease the reflection/refraction footprint of the cavity itself. Detectable hydrologic anomalies can be created by the simple drainage of groundwater into the cavity (initially saturated conditions) or by the creation of a capillary barrier around the cavity (initially unsaturated conditions). Because both processes ultimately involve unsaturated conditions we use HYDRUS 2D to numerically solve the Richard's equation and simulate flow through the vadose zone. Using the generated soil moisture information and Brutsaert's (1964) saturation-velocity relation, we constructed velocity models. Our simulations suggest several scenarios where changes in saturation due to the cavity may be utilized to enhance cavity detection with seismic waves. One simulation is for unsaturated conditions in the top 10 meters of soil, where capillary forces exert a major influence on velocity. In this case, the impedance contrast is greatest for near-saturated soils. Deeper cavities (100s of meters) in permeable saturated materials are also favorable due to the sharp impedance contrast between saturated and unsaturated material. Our hydrology-determined velocity models are then used in finite-difference wave propagation simulations to determine the effects on seismic waves at various depths and saturations

  6. Forward- vs. Inverse Problems in Modeling Seismic Attenuation

    Science.gov (United States)

    Morozov, I. B.

    2015-12-01

    Seismic attenuation is an important property of wave propagation used in numerous applications. However, the attenuation is also a complex phenomenon, and it is important to differentiate between its two typical uses: 1) in forward problems, to model the amplitudes and spectral contents of waves required for hazard assessment and geotechnical engineering, and 2) in inverse problems, to determine the physical properties of the subsurface. In the forward-problem sense, the attenuation is successfully characterized in terms of empirical parameters of geometric spreading, radiation patterns, scattering amplitudes, t-star, alpha, kappa, or Q. Arguably, the predicted energy losses can be correct even if the underlying attenuation model is phenomenological and not sufficiently based on physics. An example of such phenomenological model is the viscoelasticity based on the correspondence principle and the Q-factor assigned to the material. By contrast, when used to invert for in situ material properties, models addressing the specific physics are required. In many studies (including in this session), a Q-factor is interpreted as a property of a point within the subsurface; however this property is only phenomenological and may be physically insufficient or inconsistent. For example, the bulk or shear Q at the same point can be different when evaluated from different wave modes. The cases of frequency-dependent Q are particularly prone of ambiguities such as trade-off with the assumed background geometric spreading. To rigorously characterize the in situ material properties responsible for seismic-wave attenuation, it is insufficient to only focus on the seismic energy loss. Mechanical models of the material need to be considered. Such models can be constructed by using Lagrangian mechanics. These models should likely contain no Q but will be based on parameters of microstructure such as heterogeneity, fractures, or fluids. I illustrate several such models based on viscosity

  7. A new tomographic image on the Philippine Sea Slab beneath Tokyo - Implication to seismic hazard in the Tokyo metropolitan region -

    Science.gov (United States)

    Hirata, N.; Sakai, S.; Nakagawa, S.; Ishikawa, M.; Sato, H.; Kasahara, K.; Kimura, H.; Honda, R.

    2012-12-01

    In central Japan, the Philippine Sea plate (PSP) subducts beneath the Tokyo metropolitan region. Devastating M8-class earthquakes occurred on the upper surface of the Philippine Sea plate (SPS), examples of which are the Genroku earthquake of 1703 (magnitude M=8.0) and the Kanto earthquake of 1923 (M=7.9), which had 105,000 fatalities. A M7 or greater (M7+) earthquake in this region at present has high potential to produce devastating loss of life and property with even greater global economic repercussions although it is smaller than the megathrust type M8-class earthquakes. This great earthquake is evaluated to occur with a probability of 70 % in 30 years by the Earthquake Research Committee of Japan. The M7+ earthquakes may occur either on the upper surface or intra slab of PSP. The Central Disaster Management Council of Japan estimates the next great M7+ earthquake will cause 11,000 fatalities and 112 trillion yen (1 trillion US$) economic loss at worst case if it occur beneath northern Tokyo bay with M7.3. However, the estimate is based on a source fault model by conventional studies about the PSP geometry. To evaluate seismic hazard due to the great quake we need to clarify the geometry of PSP and also the Pacific palate (PAP) that subducs beneath PSP. We identify those plates with use of seismic tomography and available deep seismic reflection profiling and borehole data in southern Kanto area. We deployed about 300 seismic stations in the greater Tokyo urban region under the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area. We obtain clear P- and S- wave velocity (Vp and Vs) tomograms which show a clear image of PSP and PAP. A depth to the top of PSP, 20 to 30 kilometer beneath northern part of Tokyo bay, is about 10 km shallower than previous estimates based on the distribution of seismicity (Ishida, 1992). This shallower plate geometry changes estimations of strong ground motion for seismic hazards analysis within the Tokyo

  8. Recent seismicity of Italy: Active tectonics of the central Mediterranean region and seismicity rate changes after the Mw 6.3 L'Aquila earthquake

    Science.gov (United States)

    Chiarabba, Claudio; De Gori, Pasquale; Mele, Francesco Mariano

    2015-01-01

    In this paper we present a new image of the instrumental seismicity of Italy, obtained by refining hypocentral determinations for about 100,000 earthquakes that occurred in the period 2005-2012. The improved locations yield new constraints on active tectonics of the central Mediterranean area, where prolonged interaction between nested plates and continental slivers led to the development of the Alpine and Apennines systems. Intermediate-depth and deep earthquakes define a lateral heterogeneous process of delamination and sinking of the continental lithosphere active beneath the mountain belts. Shallow seismicity prevalently occurs beneath elevated topography and correlates with low velocity mantle anomalies, suggesting a superposition of gravity-related forces to the Eurasia-Africa plate convergence. The delamination process drives a paired system of compression and extension that stretches the mountain range while shortening the external side of the belts. The updated seismic catalog permits us to resolve a sharp variation of seismic rates that occurred in recent years, timely after the 2009 Mw 6.3 L'Aquila earthquake. The increase of seismic rates is reasonably due to regional-scale perturbation of the stress field induced by fluid flow and pore-pressure variations within the crust, probably related to deep dehydration processes active beneath the mountain belt.

  9. Analysis of the recent (2012-2016) seismic activity in the Guadalajara, Jalisco, Mexico region.

    Science.gov (United States)

    Yamamoto, J.

    2016-12-01

    The central part of Jalisco, Mexico has experienced at different times the occurrence of low magnitude earthquakes sequences and swarms. Although the effect of these earthquakes has been limited to relatively small areas have caused general alarm within the population and even in some cases catastrophes. These groups of earthquakes that have lasted for weeks and even months have greater importance because they affect the most populous state area including the capital city of Guadalajara. An extraordinary example of these series of earthquakes occurred on 8 May 1912 that lasted until September. In the first 18 days 64 events were felt by residents of Guadalajara and about 10 thousand people fled the city for safer places. Since then, there has been a relative seismic activity calm in the region until May 2012 in which a conspicuous seismic activity reactivation has been observed. This paper analyzes the seismic activity starting with the earthquake of May 18, 2012 (03:07 UT) occurred at the west edge of Lake Chapala until the most recent earthquake on 28 July 2016. It includes seven low magnitude earthquakes with magnitudes between 3.5 and 4.8. The analysis includes hypocentral locations revision, determination of fault mechanisms based on polarity of first arrival complemented with results of waveform inversion. Possible causal correlation with known geological structures is discussed.

  10. Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan

    Science.gov (United States)

    Shito, Azusa; Matsumoto, Satoshi; Shimizu, Hiroshi; Ohkura, Takahiro; Takahashi, Hiroaki; Sakai, Shinichi; Okada, Tomomi; Miyamachi, Hiroki; Kosuga, Masahiro; Maeda, Yuta; Yoshimi, Masayuki; Asano, Youichi; Okubo, Makoto

    2017-08-01

    We investigate seismic wave velocity structure and spatial distribution of the seismicity in the source region of the 2016 Kumamoto earthquake sequence. A one-dimensional mean velocity shows that the seismogenic zone has a high-velocity and low-Vp/Vs ratio relative to the average velocity structure of Kyushu Island. This indicates that the crust is relatively strong, capable of sustaining sufficiently high strain energy to facilitate two large (Mj > 6.5) earthquakes in close proximity to one another in rapid succession. Three-dimensional tomography of the seismogenic zone around the source of the 2016 Kumamoto earthquake sequence yields Vp = 6 km/s and Vs = 3.5 km/s. Most large-displacement areas (asperities) of the Mj 7.3 event overlap with the seismogenic zone and the overlying surface layer. Aftershock seismicity is distributed deeper than the conventional seismogenic zone, which suggests decreased strength due to fluids or increased stress, both caused by coseismic slip.

  11. Probabilistic seismic hazard study based on active fault and finite element geodynamic models

    Science.gov (United States)

    Kastelic, Vanja; Carafa, Michele M. C.; Visini, Francesco

    2016-04-01

    We present a probabilistic seismic hazard analysis (PSHA) that is exclusively based on active faults and geodynamic finite element input models whereas seismic catalogues were used only in a posterior comparison. We applied the developed model in the External Dinarides, a slow deforming thrust-and-fold belt at the contact between Adria and Eurasia.. is the Our method consists of establishing s two earthquake rupture forecast models: (i) a geological active fault input (GEO) model and, (ii) a finite element (FEM) model. The GEO model is based on active fault database that provides information on fault location and its geometric and kinematic parameters together with estimations on its slip rate. By default in this model all deformation is set to be released along the active faults. The FEM model is based on a numerical geodynamic model developed for the region of study. In this model the deformation is, besides along the active faults, released also in the volumetric continuum elements. From both models we calculated their corresponding activity rates, its earthquake rates and their final expected peak ground accelerations. We investigated both the source model and the earthquake model uncertainties by varying the main active fault and earthquake rate calculation parameters through constructing corresponding branches of the seismic hazard logic tree. Hazard maps and UHS curves have been produced for horizontal ground motion on bedrock conditions VS 30 ≥ 800 m/s), thereby not considering local site amplification effects. The hazard was computed over a 0.2° spaced grid considering 648 branches of the logic tree and the mean value of 10% probability of exceedance in 50 years hazard level, while the 5th and 95th percentiles were also computed to investigate the model limits. We conducted a sensitivity analysis to control which of the input parameters influence the final hazard results in which measure. The results of such comparison evidence the deformation model and

  12. Geological and geodynamic reconstruction of the East Barents megabasin from analysis of the 4-AR regional seismic profile

    Science.gov (United States)

    Startseva, K. F.; Nikishin, A. M.; Malyshev, N. A.; Nikishin, V. A.; Valyushcheva, A. A.

    2017-07-01

    The article considers problems related to the geological structure and geodynamic history of sedimentary basins of the Barents Sea. We analyze new seismic survey data obtained in 2005-2016 to refine the geological structure model for the study area and to render it in more detail. Based on the data of geological surveys in adjacent land (Novaya Zemlya, Franz Josef Land, and Kolguev Island), drilling, and seismic survey, we identified the following geodynamic stages of formation of the East Barents megabasin: Late Devonian rifting, the onset of postrift sinking and formation of the deep basin in Carboniferous-Permian, unique (in terms of extent) and very rapid sedimentation in the Early Triassic, continued thermal sinking with episodes of inversion vertical movements in the Middle Triassic-Early Cretaceous, folded pressure deformations that formed gently sloping anticlines in the Late Cretaceous-Cenozoic, and glacial erosion in the Quaternary. We performed paleoreconstructions for key episodes in evolution of the East Barents megabasin based on the 4-AR regional profile. From the geometric modeling results, we estimated the value of total crustal extension caused by Late Devonian rifting for the existing crustal model.

  13. Coupling a Basin Modeling and a Seismic Code using MOAB

    KAUST Repository

    Yan, Mi

    2012-06-02

    We report on a demonstration of loose multiphysics coupling between a basin modeling code and a seismic code running on a large parallel machine. Multiphysics coupling, which is one critical capability for a high performance computing (HPC) framework, was implemented using the MOAB open-source mesh and field database. MOAB provides for code coupling by storing mesh data and input and output field data for the coupled analysis codes and interpolating the field values between different meshes used by the coupled codes. We found it straightforward to use MOAB to couple the PBSM basin modeling code and the FWI3D seismic code on an IBM Blue Gene/P system. We describe how the coupling was implemented and present benchmarking results for up to 8 racks of Blue Gene/P with 8192 nodes and MPI processes. The coupling code is fast compared to the analysis codes and it scales well up to at least 8192 nodes, indicating that a mesh and field database is an efficient way to implement loose multiphysics coupling for large parallel machines.

  14. Numerical modeling of seismic waves using frequency-adaptive meshes

    Science.gov (United States)

    Hu, Jinyin; Jia, Xiaofeng

    2016-08-01

    An improved modeling algorithm using frequency-adaptive meshes is applied to meet the computational requirements of all seismic frequency components. It automatically adopts coarse meshes for low-frequency computations and fine meshes for high-frequency computations. The grid intervals are adaptively calculated based on a smooth inversely proportional function of grid size with respect to the frequency. In regular grid-based methods, the uniform mesh or non-uniform mesh is used for frequency-domain wave propagators and it is fixed for all frequencies. A too coarse mesh results in inaccurate high-frequency wavefields and unacceptable numerical dispersion; on the other hand, an overly fine mesh may cause storage and computational overburdens as well as invalid propagation angles of low-frequency wavefields. Experiments on the Padé generalized screen propagator indicate that the Adaptive mesh effectively solves these drawbacks of regular fixed-mesh methods, thus accurately computing the wavefield and its propagation angle in a wide frequency band. Several synthetic examples also demonstrate its feasibility for seismic modeling and migration.

  15. Geodetic insights on the post-seismic transients from the Andaman Nicobar region: 2005-2013

    Science.gov (United States)

    Earnest, A.; Vijayan, M.; Jade, S.; Krishnan, R.; Sringeri, S. T.

    2013-12-01

    The 2004 Mw 9.2 Sumatra-Andaman mega-thrust rupture broke the whole 1300 km long fore-arc sliver boundary of the Indo- Burmese collision. Earlier events of 1679 (M~7.5), 1941 (M 7.7), 1881 (M~7.9) and 2002 (Mw 7.3) generated spatially restricted ruptures along this margin. GPS based geodetic measurements of post-seismic deformation following the 2004 M9.2 Sumatra-Andaman earthquake gives insights on the spatio-temporal evolution of transient tectonic deformation happening at the Suda-Andaman margin. This work encompasses the near-field geodetic data collected from the Andaman-Nicobar Islands and far-field CGPS site data available from SUGAR, UNAVCO and IGS from 2005-2013. Precise geodetic data analysis shows that the GPS benchmarks in the Andaman-Nicobar region moved immediately after 2004 event towards the sea-ward trench in the SW direction, following very much the co-seismic offset directions. This can be possibly because of the continued predominant after-slip occurrence around the 2004 rupture zone due to the velocity-strengthening behavior at the downdip segments of the rupture zone. Lately a progressive reversal of motion direction away from the oceanic trench (and the co-seismic offset direction) of the coastal and inland GPS sites of Andaman-Nicobar Islands are observed. The site displacement transients shows a rotation of the displacement vector moving from south-west to north. Spatio-temporal analysis of the earthquakes show dense shallow seismicity in the back-arc region, normal and thrust faulting activity towards the trench. The hypo-central distribution highlights the shallow subduction at the northern segment, which becomes steeper and deeper to the south. The stress distribution, inferred from the P and T-axes of earthquake faulting mechanisms, represents the compressional fore-arc and extensional back-arc stress regimes. Our analysis results will be discussed in detail by integrating the kinematics and seismo-tectonic evolution of this subducting

  16. Improvements of the Regional Seismic network of Northwestern Italy in the framework of ALCoTra program activities

    Science.gov (United States)

    Bosco, Fabrizio

    2014-05-01

    ALCoTra project "CASSAT" (Coordination and Analysis of Alpine Trans-border Seismic Surveillance), we evaluate the improvement of monitoring systems performances in terms of localizations precision and number of detections. Furthermore, we update the procedures for the production of ground shaking maps, with installation of accelerometers and integration of new available data for site effects assessment (VS30 map, FA-VS30 correlations by numerical simulations of seismic response), determined for the specific regional context from geophysical surveys data and geological analysis. As a consequence of the increase of available data due to new stations installation and recently recorded events, a new local magnitude scaling law is calibrated for the area. We also develop a parametric methodology to improve network real-time localization procedures in Northwestern Italy. The area, surrounded by Western Alps and Northern Apennines, presents a complex system of lithospheric structures, characterized by strong heterogeneities of various physical parameters (Ivrea Body, subducting European lithosphere, Ligurian Sea Moho, Po Valley deposits). We work with a localization algorithm (Hypoinverse-2000) suitable for such a heterogeneous context , adopting multi-1d crustal velocities models, linked to epicentral coordinates. In this analysis, first we build velocities models integrating several available geophysical and geo-structural data; then we test jointly both models and algorithm parameters with specifically developed automatic iterative procedures, through batch scripting, database, GIS and statistical analysis tools.

  17. Seismic modeling in complex media; Modelagem sismica em meios complexos

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Eldues Oliveira [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia. Lab. de Metodos Computacionais em Engenharia (LAMCE)]. E-mail: eldues@lamce.ufrj.br; Soares Filho, Djalma M. [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas]. E-mail: djalma@cenpes.petrobras.com.br

    2003-07-01

    This work was divided in two phases: first we perform simulations in a realistic onshore model that has the presence of a thick shale layer (approx 1 km) above of a gas deposit, faults plane, vertical interfaces and relief of irregular topography. We esteem the wave-field complexity in a model with typical geology sub-Andean. In this case we applied TIV scheme. Second we simulate an offshore model that presents interfaces with high seismic impedance due to the presence of salt domes. In both simulations we compare seismograms obtained using isotropic and anisotropic layers. These comparisons show as the use of traditional tools (i.e., acoustic and isotropic) can be negligent in highly complex areas. (author)

  18. Regional seismic stratigraphy and controls on the Quaternary evolution of the Cape Hatteras region of the Atlantic passive margin, USA

    Science.gov (United States)

    Mallinson, D.J.; Culver, S.J.; Riggs, S.R.; Thieler, E.R.; Foster, D.; Wehmiller, J.; Farrell, K.M.; Pierson, J.

    2010-01-01

    Seismic and core data, combined with amino acid racemization and strontium-isotope age data, enable the definition of the Quaternary stratigraphic framework and recognition of geologic controls on the development of the modern coastal system of North Carolina, U.S.A. Seven regionally continuous high amplitude reflections are defined which bound six seismic stratigraphic units consisting of multiple regionally discontinuous depositional sequences and parasequence sets, and enable an understanding of the evolution of this margin. Data reveal the progressive eastward progradation and aggradation of the Quaternary shelf. The early Pleistocene inner shelf occurs at a depth of ca. 20-40 m beneath the western part of the modern estuarine system (Pamlico Sound). A mid- to outer shelf lowstand terrace (also early Pleistocene) with shelf sand ridge deposits comprising parasequence sets within a transgressive systems tract, occurs at a deeper level (ca. 45-70 m) beneath the modern barrier island system (the Outer Banks) and northern Pamlico Sound. Seismic and foraminiferal paleoenvironmental data from cores indicate the occurrence of lowstand strandplain shoreline deposits on the early to middle Pleistocene shelf. Middle to late Pleistocene deposits occur above a prominent unconformity and marine flooding surface that truncates underlying units, and contain numerous filled fluvial valleys that are incised into the early and middle Pleistocene deposits. The stratigraphic framework suggests margin progradation and aggradation modified by an increase in the magnitude of sea-level fluctuations during the middle to late Pleistocene, expressed as falling stage, lowstand, transgressive and highstand systems tracts. Thick stratigraphic sequences occur within the middle Pleistocene section, suggesting the occurrence of high capacity fluvial point sources debouching into the area from the west and north. Furthermore, the antecedent topography plays a significant role in the evolution

  19. Seismotectonic Investigation of Biga Peninsula in SW Marmara Region Using Steerable Filter Technique, Potential Field Data and Recent Seismicity

    Science.gov (United States)

    Görgün, Ethem; Albora, A. Muhittin

    2017-07-01

    We examine seismotectonic setting of Biga Peninsula in western Anatolia (Çanakkale region) using the steerable filter technique and recent seismicity. One of the most important issues in geophysics is to observe borders or margins of tectonic/geologic discontinues. For this purpose, we apply this filter technique to gravity anomaly map of Biga Peninsula. We observe undetected/buried faults in Biga Peninsula using the steerable technique where they have never been seen in the geological maps before. These buried faults comply with recent seismicity for this region. Focal mechanisms of past earthquakes (M ≥ 3.5) are in good agreement with fault orientations. This observation shows that we have to take into account these fault locations and consider for preparing future seismic hazard maps. The geometry of fault segments reveals mostly strike-slip faulting regime with NE-SW trending direction of T-axis in the entire study region. According to high-resolution hypocenter relocation of the Biga earthquake sequences in the observation period between 5 January 2005 and 14 November 2015 extends from N to S direction. The stress tensor inversion results indicate a predominant normal stress regime with a NW-SE oriented maximum horizontal compressive stress (S H). According to strong discrepancy of density in the Biga Peninsula is characterized by numerous small segmented secondary faults. These buried or undetected fault locations indicate that these segments are large enough to increase earthquake stress failure towards NW-SE and N-S directions, respectively. Seismotectonic setting of Biga Peninsula is divided into sub-regions by NE-SW trending secondary faults with normal and major strike-slip components. This output is verified by steerable filter and local/regional seismotectonic analysis. We propose a new seismotectonic model for Biga Peninsula and update the orientation of active fault segments. According to our model, North Anatolian Fault Zone cross-cuts the

  20. KFUPM-KAUST Red Sea model: Digital viscoelastic depth model and synthetic seismic data set

    KAUST Repository

    Al-Shuhail, Abdullatif A.

    2017-06-01

    The Red Sea is geologically interesting due to its unique structures and abundant mineral and petroleum resources, yet no digital geologic models or synthetic seismic data of the Red Sea are publicly available for testing algorithms to image and analyze the area\\'s interesting features. This study compiles a 2D viscoelastic model of the Red Sea and calculates a corresponding multicomponent synthetic seismic data set. The models and data sets are made publicly available for download. We hope this effort will encourage interested researchers to test their processing algorithms on this data set and model and share their results publicly as well.

  1. Tectonic model and seismic potential of the eastern Gulf of Alaska and Yakataga Seismic Gap

    Science.gov (United States)

    Perez, Omar J.; Jacob, Klaus H.

    1980-12-01

    Based on 13 new fault plane solutions and published seismological, geological, and geophysical data, we interpret the deformation along the Pacific-North American plate margin in the eastern Gulf of Alaska. Three major tectonic units can be distinguished: (1) the North American plate, (2) the Pacific plate, and (3) a belt of mobile borderland terranes. The Pacific plate moves in a NNW direction at rates of about 6 cm/yr in relation to the North American plate. That motion results in mostly right-lateral strike slip at the Queen Charlotte-Fairweather fault system, a well-known observation. A new finding,however, is that a small component (˜1 cm/yr) of convergence may also be present which results in minor subduction of the oceanic plate beneath portions of the continental margin. Heretofore the Queen Charlotte-Fairweather fault zone and associated continental margin was interpreted as a classical, pure transform boundary. The Yakutat block, a borderland terrane about 400 km long and 100 to 200 km wide, is carried passively by the Pacific plate except that the block slowly overrides this plate at about 1 cm/yr. This motion is taken up by almost pure thrust faulting in a southwesterly direction along a 400-km long SE striking shelf edge structure. At its NW edge the Yakutat block is in turn being thrust beneath the North American plate along the Pamplona zone-Icy Bay lineament. The underthrusting of the Yakutat block results in a major orogeny, crustal shortening and uplift of the Chugach-St. Elias range. The effects of this collision may extend as far as 500 km inland and cause some deformation at the Denali fault in the central Alaska Range. Subduction of the Pacific plate beneath the colliding margin appears responsible for development of an active volcanic arc up to 300 km inland which trends SE from the Wrangell Mountains to Yukon Territory, Canada, and perhaps to Mt. Edgecumbe volcano in southeast Alaska. The tectonic model proposed implies a high seismic

  2. Forecasting Italian seismicity through a spatio-temporal physical model: importance of considering time-dependency and reliability of the forecast

    Directory of Open Access Journals (Sweden)

    Amir Hakimhashemi

    2010-11-01

    Full Text Available We apply here a forecasting model to the Italian region for the spatio-temporal distribution of seismicity based on a smoothing Kernel function, Coulomb stress variations, and a rate-and-state friction law. We tested the feasibility of this approach, and analyzed the importance of introducing time-dependency in forecasting future events. The change in seismicity rate as a function of time was estimated by calculating the Coulomb stress change imparted by large earthquakes. We applied our approach to the region of Italy, and used all of the cataloged earthquakes that occurred up to 2006 to generate the reference seismicity rate. For calculation of the time-dependent seismicity rate changes, we estimated the rate-and-state stress transfer imparted by all of the ML≥4.0 earthquakes that occurred during 2007 and 2008. To validate the results, we first compared the reference seismicity rate with the distribution of ML≥1.8 earthquakes since 2007, using both a non-declustered and a declustered catalog. A positive correlation was found, and all of the forecast earthquakes had locations within 82% and 87% of the study area with the highest seismicity rate, respectively. Furthermore, 95% of the forecast earthquakes had locations within 27% and 47% of the study area with the highest seismicity rate, respectively. For the time-dependent seismicity rate changes, the number of events with locations in the regions with a seismicity rate increase was 11% more than in the regions with a seismicity rate decrease.

  3. Mapping basin-wide subaquatic slope failure susceptibility as a tool to assess regional seismic and tsunami hazards

    Science.gov (United States)

    Strasser, Michael; Hilbe, Michael; Anselmetti, Flavio S.

    2010-05-01

    With increasing awareness of oceanic geohazards, submarine landslides are gaining wide attention because of their catastrophic impacts on both offshore infrastructures (e.g. pipelines, cables and platforms) and coastal areas (e.g. landslide-induced tsunamis). They also are of great interest because they can be directly related to primary trigger mechanisms including earthquakes, rapid sedimentation, gas release, glacial and tidal loading, wave action, or clathrate dissociation, many of which represent potential geohazards themselves. In active tectonic environments, for instance, subaquatic landslide deposits can be used to make inferences regarding the hazard derived from seismic activity. Enormous scientific and economic efforts are thus being undertaken to better determine and quantify causes and effects of natural hazards related to subaquatic landslides. In order to achieve this fundamental goal, the detailed study of past events, the assessment of their recurrence intervals and the quantitative reconstruction of magnitudes and intensities of both causal and subsequent processes and impacts are key requirements. Here we present data and results from a study using fjord-type Lake Lucerne in central Switzerland as a "model ocean" to test a new concept for the assessment of regional seismic and tsunami hazard by basin-wide mapping of critical slope stability conditions for subaquatic landslide initiation. Previously acquired high-resolution bathymetry and reflection seismic data as well as sedimentological and in situ geotechnical data, provide a comprehensive data base to investigate subaquatic landslides and related geohazards. Available data are implemented into a basin-wide slope model. In a Geographic Information System (GIS)-framework, a pseudo-static limit equilibrium infinite slope stability equation is solved for each model point representing reconstructed slope conditions at different times in the past, during which earthquake-triggered landslides

  4. 2-D crustal Poisson's ratio from seismic travel time inversion in Changbaishan Tianchi volcanic region

    Institute of Scientific and Technical Information of China (English)

    LIU Zhi; ZHANG Xian-kang; WANG Fu-yun; DUAN Yong-hong; LAI Xiao-ling

    2005-01-01

    Based on the inversion method of 2D velocity structure and interface, the crustal velocity structures of P-wave and S-wave along the profile L1 are determined simultaneously with deep seismic sounding data in Changbaishan Tianchi volcanic region, and then its Poisson's ratio is obtained. Calculated results show that this technique overcomes some defects of traditional forward calculation method, and it is also very effective to determine Poisson's ratio distribution of deep seismic sounding profile, especially useful for study on volcanic magma and crustal fault zone. Study result indicates that there is an abnormally high Poisson's ratio body that is about 30 km wide and 12 km high in the low velocity region under Tianchi crater. Its value of Poisson's ratio is 8% higher than that of surrounding medium and it should be the magma chamber formed from melted rock with high temperature. There is a high Poisson's ratio zone ranging from magma chamber to the top of crust, which may be the uprise passage of hot substance. The lower part with high Poisson's ratio, which stretches downward to Moho, is possibly the extrusion way of hot substance from the uppermost mantle. The conclusions above are consistent with the study results of both tomographic determination of 3D crustal structure and magnetotelluric survey in this region.

  5. The contribution of the Global Change Observatory Central Asia to seismic hazard and risk assessment in the Central Asian region

    Science.gov (United States)

    Parolai, S.; Bindi, D.; Haberland, C. A.; Pittore, M.; Pilz, M.; Rosenau, M.; Schurr, B.; Wieland, M.; Yuan, X.

    2012-12-01

    are necessary. Temporary seismic networks have been installed in several Central Asian cities (Bishkek and Karakol, Kyrgyzstan; Dushanbe, Tajikistan; Tashkent, Uzbekistan) within the framework of the Earthquake Model Central Asia (EMCA), a regional program of the Global Earthquake Model (GEM). The empirically estimated site effects have already helped to improve real-time risk scenarios for Bishkek and will be applied to other major cities. - A crucial requirement for disaster risk reduction involves the analysis of the vulnerability of existing building inventories. Whereas traditional approaches are very time- and cost-consuming, and even impossible given the high rate of urbanization in Central Asian capitals, our integrated approach is based on satellite remote sensing and ground-based omni-directional imaging, providing building inventories and thus structural vulnerability over large areas (EMCA, GEM-IDCT). All mentioned activities are carried out within the framework of cooperation between GFZ and regional national institutes, in particular the Central Asian Institute for Applied Geosciences. Altogether, this comprehensive and long-term risk analyses and research program will lead to a better understanding of the coupling of endogene and exogene processes and the identification of their impact on society.

  6. Offshore double-planed shallow seismic zone in the NE Japan forearc region revealed by sP depth phases recorded by regional networks

    Science.gov (United States)

    Gamage, S.S.N.; Umino, N.; Hasegawa, A.; Kirby, S.H.

    2009-01-01

    We detected the sP depth phase at small epicentral distances of about 150 km or more in the seismograms of shallow earthquakes in the NE Japan forearc region. The focal depths of 1078 M > 3 earthquakes that occurred from 2000 to 2006 were precisely determined using the time delay of the sP phase from the initial P-wave arrival. The distribution of relocated hypocentres clearly shows the configuration of a double-planed shallow seismic zone beneath the Pacific Ocean. The upper plane has a low dip angle near the Japan Trench, increasing gradually to ???30?? at approximately 100 km landward of the Japan Trench. The lower plane is approximately parallel to the upper plane, and appears to be the near-trench counterpart of the lower plane of the double-planed deep seismic zone beneath the land area. The distance between the upper and lower planes is 28-32 km, which is approximately the same as or slightly smaller than that of the double-planed deep seismic zone beneath the land area. Focal mechanism solutions of the relocated earthquakes are determined from P-wave initial motion data. Although P-wave initial motion data for these offshore events are not ideally distributed on the focal sphere, we found that the upper-plane events that occur near the Japan Trench are characterized by normal faulting, whereas lower-plane events are characterized by thrust faulting. This focal mechanism distribution is the opposite to that of the double-planed deep seismic zone beneath the land area. The characteristics of these focal mechanisms for the shallow and deep doubled-planed seismic zones can be explained by a bending-unbending model of the subducting Pacific plate. Some of relocated earthquakes took place in the source area of the 1933 Mw8.4 Sanriku earthquake at depths of 10-23 km. The available focal mechanisms for these events are characterized by normal faulting. Given that the 1933 event was a large normal-fault event that occurred along a fault plane dipping landward, the

  7. Aftershock seismicity of the 2010 Maule Mw=8.8 Chile, earthquake: Correlation between co-seismic slip models and aftershock distribution?

    Science.gov (United States)

    Rietbrock, A.; Ryder, I.; Hayes, G.; Haberland, C.; Comte, D.; Roecker, S.

    2012-01-01

    The 27 February 2010 Maule, Chile (Mw=8.8) earthquake is one of the best instrumentally observed subduction zone megathrust events. Here we present locations, magnitudes and cumulative equivalent moment of the first -2 months of aftershocks, recorded on a temporary network deployed within 2 weeks of the occurrence of the mainshock. Using automatically-determined onset times and a back projection approach for event association, we are able to detect over 30,000 events in the time period analyzed. To further increase the location accuracy, we systematically searched for potential S-wave arrivals and events were located in a regional 2D velocity model. Additionally, we calculated regional moment tensors to gain insight into the deformation history of the aftershock sequence. We find that the aftershock seismicity is concentrated between 40 and 140 km distance from the trench over a depth range of 10 to 35 km. Focal mechanisms indicate a predominance of thrust faulting, with occasional normal faulting events. Increased activity is seen in the outer-rise region of the Nazca plate, predominantly in the northern part of the rupture area. Further down-dip, a second band of clustered seismicity, showing mainly thrust motion, is located at depths of 40–45 km. By comparing recent published mainshock source inversions with our aftershock distribution, we discriminate slip models based on the assumption that aftershocks occur in areas of rapid transition between high and low slip, surrounding high-slip regions of the mainshock.

  8. Problems of seismic hazard estimation in regions with few large earthquakes: Examples from eastern Canada

    Science.gov (United States)

    Basham, P. W.; Adams, John

    1989-10-01

    Seismic hazard estimates and seismic zoning maps are based on an assessment of historical and recent seismieity and any correlations with geologic and tectonic features that might define the earthquake potential. Evidence is accumulating that the large earthquakes in eastern Canada ( M ~ 7) may be associated with the rift systems hat surround or break the integrity of the North American craton. The problem for seismic hazard estimation is that the larger historical earthquakes are not uniformly distributed along the Paleozoic St. Lawrence-Ottawa rift system and are too rare on the Mesozoic eastern margin rift to assess the overall seismogenic potential. Multiple source zone models for hazard estimation could include hypotheses of future M = 7 earthquakes at any location along these rift systems, but at a moderate probability (such as that used in the Canadian zoning maps) the resultant hazard will be so diluted that it will not result in adequate design against the near-source effects of such earthquakes. The near-source effects of large, rare earthquakes can, however, be accommodated in conservative codes and standards for critical facilities, if society is willing to pay the price.

  9. Analysis of the induced seismicity of the Lacq gas field (Southwestern France) and model of deformation

    Science.gov (United States)

    Bardainne, T.; Dubos-Sallée, N.; Sénéchal, G.; Gaillot, P.; Perroud, H.

    2008-03-01

    The goal of this paper is to propose a model of deformation pattern for the Lacq gas field (southwest of France), considering the temporal and spatial evolution of the observed induced seismicity. This model of deformation has been determined from an updating of the earthquake locations and considering theoretical and analogue models usually accepted for hydrocarbon field deformation. The Lacq seismicity is clearly not linked to the natural seismicity of the Pyrenean range recorded 30km farther to the south since the first event was felt in 1969, after the beginning of the hydrocarbon recovery. From 1974 to 1997, more than 2000 local events (ML organized seismicity occurred where fault orientation is consistent with the poroelastic stress perturbation due to the gas recovery. On the contrary, the seismicity is quiescient where isobaths of the reservoir roof are closed to be perpendicular to the faults. These quiescient areas as well as the central seismic part are characterized by a surface subsidence determined by repeated levelling profiles. Moreover, the temporal evolution of the distribution of the seismicity clearly exhibits a spatial migration from the centre to the boundaries of the reservoir. We conclude that the entire field is strained but this deformation is seismically expressed only where faults are parallel to the isobaths of the reservoir roof and where these faults plunge towards outside the field according to one of the two theoretical deformation models considered in our study. Then we propose a temporal scenario of deformation along the principal axis of seismic deformation.

  10. Quick regional centroid moment tensor solutions for the Emilia 2012 (northern Italy seismic sequence

    Directory of Open Access Journals (Sweden)

    Silvia Pondrelli

    2012-10-01

    Full Text Available In May 2012, a seismic sequence struck the Emilia region (northern Italy. The mainshock, of Ml 5.9, occurred on May 20, 2012, at 02:03 UTC. This was preceded by a smaller Ml 4.1 foreshock some hours before (23:13 UTC on May 19, 2012 and followed by more than 2,500 earthquakes in the magnitude range from Ml 0.7 to 5.2. In addition, on May 29, 2012, three further strong earthquakes occurred, all with magnitude Ml ≥5.2: a Ml 5.8 earthquake in the morning (07:00 UTC, followed by two events within just 5 min of each other, one at 10:55 UTC (Ml 5.3 and the second at 11:00 UTC (Ml 5.2. For all of the Ml ≥4.0 earthquakes in Italy and for all of the Ml ≥4.5 in the Mediterranean area, an automatic procedure for the computation of a regional centroid moment tensor (RCMT is triggered by an email alert. Within 1 h of the event, a manually revised quick RCMT (QRCMT can be published on the website if the solution is considered stable. In particular, for the Emilia seismic sequence, 13 QRCMTs were determined and for three of them, those with M >5.5, the automatically computed QRCMTs fitted the criteria for publication without manual revision. Using this seismic sequence as a test, we can then identify the magnitude threshold for automatic publication of our QRCMTs.

  11. Automated seismic detection of landslides at regional scales: a Random Forest based detection algorithm for Alaska and the Himalaya.

    Science.gov (United States)

    Hibert, Clement; Malet, Jean-Philippe; Provost, Floriane; Michéa, David; Geertsema, Marten

    2017-04-01

    Detection of landslide occurrences and measurement of their dynamics properties during run-out is a high research priority but a logistical and technical challenge. Seismology has started to help in several important ways. Taking advantage of the densification of global, regional and local networks of broadband seismic stations, recent advances now permit the seismic detection and location of landslides in near-real-time. This seismic detection could potentially greatly increase the spatio-temporal resolution at which we study landslides triggering, which is critical to better understand the influence of external forcings such as rainfalls and earthquakes. However, detecting automatically seismic signals generated by landslides still represents a challenge, especially for events with volumes below one millions of cubic meters. The low signal-to-noise ratio classically observed for landslide-generated seismic signals and the difficulty to discriminate these signals from those generated by regional earthquakes or anthropogenic and natural noises are some of the obstacles that have to be circumvented. We present a new method for automatically constructing instrumental landslide catalogues from continuous seismic data. We developed a robust and versatile solution, which can be implemented in any context where a seismic detection of landslides or other mass movements is relevant. The method is based on a spectral detection of the seismic signals and the identification of the sources with a Random Forest algorithm. The spectral detection allows detecting signals with low signal-to-noise ratio, while the Random Forest algorithm achieve a high rate of positive identification of the seismic signals generated by landslides and other seismic sources. We present here the preliminary results of the application of this processing chain in two contexts: i) In Himalaya with the data acquired between 2002 and 2005 by the Hi-Climb network; ii) In Alaska using data recorded by the

  12. A tri-stage cluster identification model for accurate analysis of seismic catalogs

    Directory of Open Access Journals (Sweden)

    S. J. Nanda

    2013-02-01

    Full Text Available In this paper we propose a tri-stage cluster identification model that is a combination of a simple single iteration distance algorithm and an iterative K-means algorithm. In this study of earthquake seismicity, the model considers event location, time and magnitude information from earthquake catalog data to efficiently classify events as either background or mainshock and aftershock sequences. Tests on a synthetic seismicity catalog demonstrate the efficiency of the proposed model in terms of accuracy percentage (94.81% for background and 89.46% for aftershocks. The close agreement between lambda and cumulative plots for the ideal synthetic catalog and that generated by the proposed model also supports the accuracy of the proposed technique. There is flexibility in the model design to allow for proper selection of location and magnitude ranges, depending upon the nature of the mainshocks present in the catalog. The effectiveness of the proposed model also is evaluated by the classification of events in three historic catalogs: California, Japan and Indonesia. As expected, for both synthetic and historic catalog analysis it is observed that the density of events classified as background is almost uniform throughout the region, whereas the density of aftershock events are higher near the mainshocks.

  13. Microseismicity, Tectonics and Seismic Potential in the Western Himalayan Segment, NW Himalaya (india) Region

    Science.gov (United States)

    Kumar, S.; Parija, M. P.; Biswal, S.

    2016-12-01

    The NW Himalaya (India) region covering Garhwal and Himachal province of India is characterised by sustained seismicity during the past decades. We have relocated 423 earthquakes in the NW Himalaya between 2004 and 2013 using more than 4495 P and 4453 S accurate P and S differential travel-times. We also have determined moment tensors for 8 (Mw >= 4.0) of these earthquakes using their broadband regional waveforms. The geometry of the MHT plane has also been deduced in this study which varies along the strike of the Himalaya in flat and ramp segments with a dip range from 4° to 19° below the HFT in south to STD in the north. There are also two crustal ramps reported from this study having a depth variance below the MCT and STD between 12 to 22 km and 28 to 40 km depth respectively. The earthquake potential prevailing in the western Himalaya seismic gap that lies between the epicentral zone of the 1905 Kangra earthquake and the 1975 Kinnaur earthquake has also been estimated and it is inferred that the total amount of energy released since the last great event is only a fraction (3-5%) of the accommodated energy (95-98%) i.e. if an earthquake hits this NW Himalayan segment in future it's magnitude can be equivalent to a Mw³ 8.0. So the energy dissipated through previous earthquakes is not sufficient to prevent an upcoming giant event.

  14. Study of the Seismic Cycle of large Earthquakes in central Peru: Lima Region

    Science.gov (United States)

    Norabuena, E. O.; Quiroz, W.; Dixon, T. H.

    2009-12-01

    Since historical times, the Peruvian subduction zone has been source of large and destructive earthquakes. The more damaging one occurred on May 30 1970 offshore Peru’s northern city of Chimbote with a death toll of 70,000 people and several hundred US million dollars in property damage. More recently, three contiguous plate interface segments in southern Peru completed their seismic cycle generating the 1996 Nazca (Mw 7.1), the 2001 Atico-Arequipa (Mw 8.4) and the 2007 Pisco (Mw 7.9) earthquakes. GPS measurements obtained between 1994-2001 by IGP-CIW an University of Miami-RSMAS on the central Andes of Peru and Bolivia were used to estimate their coseismic displacements and late stage of interseismic strain accumulation. However, we focus our interest in central Peru-Lima region, which with its about 9’000,000 inhabitants is located over a locked plate interface that has not broken with magnitude Mw 8 earthquakes since May 1940, September 1966 and October 1974. We use a network of 11 GPS monuments to estimate the interseismic velocity field, infer spatial variations of interplate coupling and its relation with the background seismicity of the region.

  15. The Scandinavian regional model

    DEFF Research Database (Denmark)

    Torfing, Jacob; Lidström, Anders; Røiseland, Asbjørn

    2015-01-01

    This article maps how the sub-national regional levels of governance in Denmark, Norway and Sweden have changed from a high degree of institutional convergence to a pattern of institutional divergence. It analyses the similarities and differences in the changes in regional governance and discusses...

  16. Multi-hole seismic modeling in 3-D space and cross-hole seismic tomography analysis for boulder detection

    Science.gov (United States)

    Cheng, Fei; Liu, Jiangping; Wang, Jing; Zong, Yuquan; Yu, Mingyu

    2016-11-01

    A boulder stone, a common geological feature in south China, is referred to the remnant of a granite body which has been unevenly weathered. Undetected boulders could adversely impact the schedule and safety of subway construction when using tunnel boring machine (TBM) method. Therefore, boulder detection has always been a key issue demanded to be solved before the construction. Nowadays, cross-hole seismic tomography is a high resolution technique capable of boulder detection, however, the method can only solve for velocity in a 2-D slice between two wells, and the size and central position of the boulder are generally difficult to be accurately obtained. In this paper, the authors conduct a multi-hole wave field simulation and characteristic analysis of a boulder model based on the 3-D elastic wave staggered-grid finite difference theory, and also a 2-D imaging analysis based on first arrival travel time. The results indicate that (1) full wave field records could be obtained from multi-hole seismic wave simulations. Simulation results describe that the seismic wave propagation pattern in cross-hole high-velocity spherical geological bodies is more detailed and can serve as a basis for the wave field analysis. (2) When a cross-hole seismic section cuts through the boulder, the proposed method provides satisfactory cross-hole tomography results; however, when the section is closely positioned to the boulder, such high-velocity object in the 3-D space would impact on the surrounding wave field. The received diffracted wave interferes with the primary wave and in consequence the picked first arrival travel time is not derived from the profile, which results in a false appearance of high-velocity geology features. Finally, the results of 2-D analysis in 3-D modeling space are comparatively analyzed with the physical model test vis-a-vis the effect of high velocity body on the seismic tomographic measurements.

  17. Using a coupled hydro-mechanical fault model to better understand the risk of induced seismicity in deep geothermal projects

    Science.gov (United States)

    Abe, Steffen; Krieger, Lars; Deckert, Hagen

    2017-04-01

    The changes of fluid pressures related to the injection of fluids into the deep underground, for example during geothermal energy production, can potentially reactivate faults and thus cause induced seismic events. Therefore, an important aspect in the planning and operation of such projects, in particular in densely populated regions such as the Upper Rhine Graben in Germany, is the estimation and mitigation of the induced seismic risk. The occurrence of induced seismicity depends on a combination of hydraulic properties of the underground, mechanical and geometric parameters of the fault, and the fluid injection regime. In this study we are therefore employing a numerical model to investigate the impact of fluid pressure changes on the dynamics of the faults and the resulting seismicity. The approach combines a model of the fluid flow around a geothermal well based on a 3D finite difference discretisation of the Darcy-equation with a 2D block-slider model of a fault. The models are coupled so that the evolving pore pressure at the relevant locations of the hydraulic model is taken into account in the calculation of the stick-slip dynamics of the fault model. Our modelling approach uses two subsequent modelling steps. Initially, the fault model is run by applying a fixed deformation rate for a given duration and without the influence of the hydraulic model in order to generate the background event statistics. Initial tests have shown that the response of the fault to hydraulic loading depends on the timing of the fluid injection relative to the seismic cycle of the fault. Therefore, multiple snapshots of the fault's stress- and displacement state are generated from the fault model. In a second step, these snapshots are then used as initial conditions in a set of coupled hydro-mechanical model runs including the effects of the fluid injection. This set of models is then compared with the background event statistics to evaluate the change in the probability of

  18. Mathematical model of the seismic electromagnetic signals (SEMS) in non crystalline substances

    Energy Technology Data Exchange (ETDEWEB)

    Dennis, L. C. C.; Yahya, N.; Daud, H.; Shafie, A. [Electromagnetic cluster, Universiti Teknologi Petronas, 31750 Tronoh, Perak (Malaysia)

    2012-09-26

    The mathematical model of seismic electromagnetic waves in non crystalline substances is developed and the solutions are discussed to show the possibility of improving the electromagnetic waves especially the electric field. The shear stress of the medium in fourth order tensor gives the equation of motion. Analytic methods are selected for the solutions written in Hansen vector form. From the simulated SEMS, the frequency of seismic waves has significant effects to the SEMS propagating characteristics. EM waves transform into SEMS or energized seismic waves. Traveling distance increases once the frequency of the seismic waves increases from 100% to 1000%. SEMS with greater seismic frequency will give seismic alike waves but greater energy is embedded by EM waves and hence further distance the waves travel.

  19. Preliminary deformation model for National Seismic Hazard map of Indonesia

    Energy Technology Data Exchange (ETDEWEB)

    Meilano, Irwan; Gunawan, Endra; Sarsito, Dina; Prijatna, Kosasih; Abidin, Hasanuddin Z. [Geodesy Research Division, Faculty of Earth Science and Technology, Institute of Technology Bandung (Indonesia); Susilo,; Efendi, Joni [Agency for Geospatial Information (BIG) (Indonesia)

    2015-04-24

    Preliminary deformation model for the Indonesia’s National Seismic Hazard (NSH) map is constructed as the block rotation and strain accumulation function at the elastic half-space. Deformation due to rigid body motion is estimated by rotating six tectonic blocks in Indonesia. The interseismic deformation due to subduction is estimated by assuming coupling on subduction interface while deformation at active fault is calculated by assuming each of the fault‘s segment slips beneath a locking depth or in combination with creeping in a shallower part. This research shows that rigid body motion dominates the deformation pattern with magnitude more than 15 mm/year, except in the narrow area near subduction zones and active faults where significant deformation reach to 25 mm/year.

  20. High-resolution 3D seismic model of the crustal and uppermost mantle structure in Poland

    Science.gov (United States)

    Grad, Marek; Polkowski, Marcin; Ostaficzuk, Stanisław R.

    2016-01-01

    In the area of Poland a contact between the Precambrian and Phanerozoic Europe and the Carpathians has a complicated structure and a complex P-wave velocity of the sedimentary cover, crystalline crust, Moho depth and the uppermost mantle. The geometry of the uppermost several kilometers of sediments is relatively well recognized from over 100,000 boreholes. The vertical seismic profiling (VSP) from 1188 boreholes provided detailed velocity data for regional tectonic units and for stratigraphic successions from Permian to the Tertiary and Quaternary deposits. These data, however, do not provide information about the velocity and basement depth in the central part of the Trans-European suture zone (TESZ) and in the Carpathians. So, the data set is supplemented by 2D velocity models from 32 deep seismic sounding refraction profiles which also provide information about the crust and uppermost mantle. Together with the results of other methods: vertical seismic profiling, magnetotelluric, allow for the creation of a detailed, high-resolution 3D model for the entire Earth's crust and the uppermost mantle down to a depth of 60 km. The thinnest sedimentary cover in the Mazury-Belarus anteclise is only 0.3 to 1 km thick, which increases to 7 to 8 km along the East European Craton (EEC) margin, and 9 to 12 km in the TESZ. The Variscan domain is characterized by a 1-4 km thick sedimentary cover, while the Carpathians are characterized by very thick sedimentary layers, up to about 20 km. The crystalline crust is differentiated and has a layered structure. The crust beneath the West European Platform (WEP; Variscan domain) is characterized by P-wave velocities of 5.8-6.6 km/s. The upper and middle crusts beneath the EEC are characterized by velocities of 6.1-6.6 km/s, and are underlain by a high velocity lower crust with a velocity of about 7 km/s. A general decrease in velocity is observed from the older to the younger tectonic domains. The TESZ is associated with a steep dip

  1. Challenges in seismic hazard assessment: Analyses of ground motion modelling and seismotectonic sources

    OpenAIRE

    Sørensen, Mathilde Bøttger

    2006-01-01

    Seismic hazard assessment has an important societal impact in describing levels of ground motions to be expected in a given region in the future. Challenges in seismic hazard assessment are closely associated with the fact that different regions, due to their differences in seismotectonics setting (and hence in earthquake occurrence) as well as socioeconomic conditions, require different and innovative approaches. One of the most important aspects in this regard is the seismici...

  2. Mixture of a seismicity model based on the rate-and-state friction and ETAS model

    Science.gov (United States)

    Iwata, T.

    2015-12-01

    Currently the ETAS model [Ogata, 1988, JASA] is considered to be a standard model of seismicity. However, because the ETAS model is a purely statistical one, the physics-based seismicity model derived from the rate-and-state friction (hereafter referred to as Dieterich model) [Dieterich, 1994, JGR] is frequently examined. However, the original version of the Dieterich model has several problems in the application to real earthquake sequences and therefore modifications have been conducted in previous studies. Iwata [2015, Pageoph] is one of such studies and shows that the Dieterich model is significantly improved as a result of the inclusion of the effect of secondary aftershocks (i.e., aftershocks caused by previous aftershocks). However, still the performance of the ETAS model is superior to that of the improved Dieterich model. For further improvement, the mixture of the Dieterich and ETAS models is examined in this study. To achieve the mixture, the seismicity rate is represented as a sum of the ETAS and Dieterich models of which weights are given as k and 1-k, respectively. This mixture model is applied to the aftershock sequences of the 1995 Kobe and 2004 Mid-Niigata sequences which have been analyzed in Iwata [2015]. Additionally, the sequence of the Matsushiro earthquake swarm in central Japan 1965-1970 is also analyzed. The value of k and parameters of the ETAS and Dieterich models are estimated by means of the maximum likelihood method, and the model performances are assessed on the basis of AIC. For the two aftershock sequences, the AIC values of the ETAS model are around 3-9 smaller (i.e., better) than those of the mixture model. On the contrary, for the Matsushiro swarm, the AIC value of the mixture model is 5.8 smaller than that of the ETAS model, indicating that the mixture of the two models results in significant improvement of the seismicity model.

  3. MatSeis and the GNEM R&E regional seismic anaylsis tools.

    Energy Technology Data Exchange (ETDEWEB)

    Chael, Eric Paul; Hart, Darren M.; Young, Christopher John; Merchant, Bion John

    2003-08-01

    To improve the nuclear event monitoring capability of the U.S., the NNSA Ground-based Nuclear Explosion Monitoring Research & Engineering (GNEM R&E) program has been developing a collection of products known as the Knowledge Base (KB). Though much of the focus for the KB has been on the development of calibration data, we have also developed numerous software tools for various purposes. The Matlab-based MatSeis package and the associated suite of regional seismic analysis tools were developed to aid in the testing and evaluation of some Knowledge Base products for which existing applications were either not available or ill-suited. This presentation will provide brief overviews of MatSeis and each of the tools, emphasizing features added in the last year. MatSeis was begun in 1996 and is now a fairly mature product. It is a highly flexible seismic analysis package that provides interfaces to read data from either flatfiles or an Oracle database. All of the standard seismic analysis tasks are supported (e.g. filtering, 3 component rotation, phase picking, event location, magnitude calculation), as well as a variety of array processing algorithms (beaming, FK, coherency analysis, vespagrams). The simplicity of Matlab coding and the tremendous number of available functions make MatSeis/Matlab an ideal environment for developing new monitoring research tools (see the regional seismic analysis tools below). New MatSeis features include: addition of evid information to events in MatSeis, options to screen picks by author, input and output of origerr information, improved performance in reading flatfiles, improved speed in FK calculations, and significant improvements to Measure Tool (filtering, multiple phase display), Free Plot (filtering, phase display and alignment), Mag Tool (maximum likelihood options), and Infra Tool (improved calculation speed, display of an F statistic stream). Work on the regional seismic analysis tools (CodaMag, EventID, PhaseMatch, and Dendro

  4. Proceedings of Conference XIII, evaluation of regional seismic hazards and risk

    Science.gov (United States)

    Charonnat, Barbara B.

    1981-01-01

    The participants in the conference concluded that a great deal of useful research has been performed in the national Earthquake Hazards Reduction Program by USGS and non-USGS scientists and engineers and that the state-of-knowledge concerning the evaluation of seismic hazards and risk has been advanced substantially. Many of the technical issues raised during the conference are less controversial now because of new information and insights gained during the first three years of the expanded research program conducted under the Earthquake Hazards Reduction Act. Utilization of research results by many groups of users has also improved during this period and further improvement in utilization appears likely. Additional research is still required to resolve more completely the many complex technical issues summarized above and described in the papers contained in the proceedings. Improved certainty of research results on the evaluation of regional seismic hazards and risk is required before full utilization can be made by state and local governments who deal. with people frequently having a different perception of the hazard and its risk to them than that perceived by scientists or engineers. Each of the papers contained in the proceedings contain throughtful recommendations for improving the state-of-knowledge. Two papers, in particular, focussed on this particular theme. The first was presented by Lynn Sykes in the Geologic Keynote Address. He identified geographic areas throughout the world which may be considered as counterparts or analogues of seismic zones in the United States. He concluded that much can be learned about prediction, tectonic settings, earthquake hazards, and earthquake risk for sites in the United States by studying their tectonic analogues in other countries. The second paper was presented by John Blume in the Engineering Keynote Address. He suggested 20 specific research topics that, in his opinion, will significantly advance the state

  5. A Fault-based Crustal Deformation Model for UCERF3 and Its Implication to Seismic Hazard Analysis

    Science.gov (United States)

    Zeng, Y.; Shen, Z.

    2012-12-01

    shear zone and northern Walker Lane. This implies a significant increase in seismic hazard in the eastern California and northern Walker Lane region, but decreased seismic hazard in the southern San Andreas area, relative to the current model used in the USGS 2008 seismic hazard map evaluation. Overall the geodetic model suggests an increase in total regional moment rate of 24% compared with the UCERF2 model and the 150-yr California earthquake catalog. However not all the increases are seismic so the seismic/aseismic slip rate ratios are critical for future seismic hazard assessment.

  6. Refinement of Regional Distance Seismic Moment Tensor and Uncertainty Analysis for Source-Type Identification

    Science.gov (United States)

    2014-09-02

    as volcanic environments and geothermal systems, and other manmade shallow seismicity related to anthropogenic activities such as hydraulic...M. Larson (2007), Seismically and geodetically determined non-double couple source mechanisms from the Miyakejima volcanic earthquake swarm, J

  7. Seismic Structure and Geodynamic Evolution of the Lithosphere and Upper Mantle in the Pannonian - Carpathian Region

    Science.gov (United States)

    Houseman, G.; Stuart, G.; Dando, B.; Hetenyi, G.; Lorinczi, P.; Brueckl, E.; Hegedus, E.; Radovanovic, S.; Brisbourne, A.

    2009-04-01

    The Pannonian Basin is the largest of a group of Miocene-age extensional basins within the arc of the Alpine-Carpathian Mountain Ranges. These basins are extensional in origin, but the surrounding Carpathians result from sustained convergence during and since the period of active extension. A significant part of the mantle lithosphere here has been replaced, as gravitational instability caused an overturn of the upper mantle. The Carpathian Basins Project (CBP) is a major international broadband seismology experiment, supported by geodynamical modelling and designed to improve our understanding of the structure and evolution of the lithosphere and upper mantle beneath the Pannonian and Vienna Basins. Between 2005 and 2007 we deployed 56 portable broadband seismic stations in Austria, Hungary and Serbia, spanning the Vienna Basin and the western part of the Pannonian Basin. Arrival time residuals from teleseismic earthquakes are delayed by about 0.8 sec in the Vienna Basin and early by a similar amount in southwest Hungary. Tomographic inversion of the travel time residuals shows relatively fast P-wave velocities in the upper mantle beneath the western Pannonian Basin and slow P-wave velocities beneath the West Carpathians. Seismic anisotropy (SKS) measurements reveal an intriguing pattern of lithospheric anisotropy: in the north-west the fast direction is generally elongated EW, perpendicular to the shortening direction across the Alps. Across the Vienna Basin the fast direction is NW-SE, perpendicular to the major bounding fault systems. Across the Pannonian Basin the dominant fast direction is EW, but in several locations the vectors are rotated toward NW-SE. The Mid-Hungarian Line, a major strike-slip structure already clearly identified in the gravity field, also is associated with abrupt changes in the azimuth of lithospheric anisotropy. Receiver function analysis of the seismic discontinuity at 670 km shows significant structure on scales of order 100 km, and

  8. Fundamental aspects of the integration of seismic monitoring with numerical modelling.

    CSIR Research Space (South Africa)

    Mendecki, AJ

    2001-06-01

    Full Text Available Numerical modelling of rock-mass response to underground excavations is of vital importance for the decision-making process in designing and running a mine. Likewise, seismic monitoring with state-of-the-art local seismic systems is indispensable...

  9. Experimental determination of LMFBR seismic equivalent core model

    Energy Technology Data Exchange (ETDEWEB)

    Fontaine, B.; Buland, P.; Fegeant, O.; Gantenbein, F. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1995-12-31

    The main phenomena which influence an LMFBR core seismic response are the fluid structure interaction and the impacts between subassemblies. To study the core behaviour seismic tests and calculations have been performed on the core mock-up RAPSODIE in air or in water and for different excitation levels. (author). 2 refs., 6 figs.

  10. Subduction Zone Geometry and Pre-seismic Tectonic Constraints From the Andaman Micro- plate Region.

    Science.gov (United States)

    Earnest, A.; Freymueller, J. T.; Rajendran, K.; C. P, R.

    2007-12-01

    The 2004 Sumatra-Andaman mega-thrust rupture broke along the narrow fore-arc sliver boundary of the Indo- Burmese collision. Earlier events of 1679 (M~7.5), 1941 (M 7.7), 1881 (M~7.9) and 2002 (Mw 7.3) generated spatially restricted ruptures along this margin. Spatio-temporal analysis of the pre-seismic earthquakes showed dense seismicity in the back-arc region but negligible activity towards the trench. The hypocentral distribution highlights the shallow subduction at the northern segment, which becomes steeper and deeper to the south. The pre-earthquake stress distribution, inferred from the P and T-axes of earthquake faulting mechanisms, represents the compressional fore-arc and extensional back-arc stress regimes. Shallow NNE-SSW under- thrusting and NNW-SSE opening up of the marginal sea basin stresses were observed and this trend changes to NE-SW to N-S at intermediate depths. We collected three epochs of campaign mode GPS data along the arc from May 2002 to September 2004. These observations show nearly pure convergence along the Andaman trench prior to the earthquake. During this period the GPS sites moved westward relative to India at ~5.5 mm/yr, consistent with the earlier results. Along arc GPS velocity vectors suggest that the Andaman trench is part of a purely slip partitioned boundary, with the strike- slip component of the India-Sunda relative plate motion being taken up on the transform fault in the Andaman Sea or on the West Andaman Fault, and the convergent component on the Andaman trench. Although near normal convergence was observed, it sampled only a fraction of a possible full Andaman microplate convergence velocity, because elastic deformation from the locked shallow megathrust caused displacements toward the overriding plate, that is, away from India. Based on the Indian plate velocity and Andaman spreading rates, this component amounts to ~85% of the pre-seismic convergence. These geodetic velocities represent the present day geologic

  11. Time-clustering analysis of the 1978–2008 sub-crustal seismicity of Vrancea region

    Directory of Open Access Journals (Sweden)

    L. Telesca

    2011-08-01

    Full Text Available The analysis of time-clustering behaviour of the sub-crustal seismicity (depth larger than 60 km of the Vrancea region has been performed. The time span of the analyzed catalogue is from 1978 to 2008, and only the events with a magnitude of Mw ≥ 3 have been considered. The analysis, carried out on the full and aftershock-depleted catalogues, was performed using the Allan Factor (AF that allows the identificatiion and quantification of correlated temporal structures in temporal point processes. Our results, whose significance was analysed by means of two methods of generation of surrogate series, reveal the presence of time-clustering behaviour in the temporal distribution of seismicity data of the full catalogue. The analysis performed on the aftershock-depleted catalogue indicates that the time-clustering is associated mainly to the aftershocks generated by the two largest events occurred on 30 August 1986 (Mw = 7.1 and 30 May 1990 (Mw = 6.9.

  12. Equivalent Kelvin Impact Model for Seismic Pounding Analysis of Bridges

    Institute of Scientific and Technical Information of China (English)

    DING Yang; YUE Fuqing; LI Zhongxian

    2006-01-01

    Based on Hertz contact theory,a method to determine the parameters of Kelvin impact model for seismic pounding analysis of bridges is proposed.The impact stiffness of Kelvin model is determined by the ratio of maximum impact force to maximum contact deformation,which is calculated based on Hertz contact theory with considering the vibration effect.The restitution coefficient which has great influence on the damping coefficient of Kelvin impact model is investigated by numerical analysis.Numerical results indicate that the impact stiffness of Kelvin impact model increases with the increment of the Hertz contact stiffness,approaching velocity or the length ratio of short to long girders.Vibration effect has remarkable influence on the impact stiffness and cannot be neglected.The restitution coefficient decreases when approaching velocity increases or the length ratio of short girder to long girder decreasing.The practical ranges of impact stiffness and restitution coefficient are obtained as 3 × 108-6 × 108 N/m and 0.6-0.95 respectively.

  13. Seismic time-lapse monitoring of potential gas hydrate dissociation around boreholes : could it be feasible? A conceptual 2D study linking geomechanical and seismic FD models

    Energy Technology Data Exchange (ETDEWEB)

    Pecher, I.; Yang, J.; Anderson, R.; Tohidi, B.; MacBeth, C. [Heriot-Watt Univ., Edinburgh (United Kingdom). Inst. of Petroleum Engineering; Freij-Ayoub, R.; Clennell, B. [CSIRO Petroleum, Bentley, WA (Australia)

    2008-07-01

    Dissociation of gas hydrate to water and potentially overpressured gas around boreholes may pose a hazard for deep-water hydrocarbon production. Strategies to mitigate this risk include monitoring for early detection of dissociation. Seismic methods are especially promising, primarily because of a high sensitivity of P-wave velocity to gas in the pore space of unconsolidated sediments. This paper presented a study that applied commonly used rock physics modeling to predict the seismic response to gas hydrate dissociation with a focus on P-impedance and performed sensitivity tests. The geomechanical model was translated into seismic models. In order to determine which parameters needed to be particularly well calibrated in experimental and modeling studies, the sensitivity of seismic properties to a variation of input parameters was estimated. The seismic response was predicted from dissociating gas hydrates using two-dimensional finite-difference wave-propagation modeling to demonstrate that despite the small predicted lateral extent of hydrate dissociation, its pronounced effect on seismic properties should allow detection with a seismic source on a drilling platform and receivers on the seafloor. The paper described the methods, models, and results of the study. It was concluded that the key factors for predicting the seismic response of sediments to hydrate dissociation were the mode of gas hydrate distribution, gas distribution in the sediments, gas saturation, and pore pressure. 33 refs., 3 tabs., 8 figs.

  14. Microscale modeling of fluid flow-geomechanics-seismicity: Relationship between permeability and seismic source response in deformed rock joints

    Science.gov (United States)

    Raziperchikolaee, S.; Alvarado, V.; Yin, S.

    2014-09-01

    Studying rock joint deformation including both slippage and opening mechanisms provides an opportunity to investigate the connection between the permeability and seismic source mechanisms. A microscale fluid flow-geomechanics-seismicity model was built to evaluate the transport response and failure mechanism of microcracks developed along a joint in Berea sandstone samples during deformation. The modeling method considers comprehensive grain-cement interactions. Fluid flow behavior is obtained through a realistic network model of the pore space in the compacted assembly. The geometric description of the complex pore structure is characterized to predict permeability of the rock sample as a function of rock deformation by using a dynamic pore network model. As a result of microcracks development, forces and displacements in grains involved in bond breakage are measured to determine seismic moment tensor. Shear and nonshear displacements are applied to the joint samples to investigate their effects on permeability evolution and failure mechanism of microcracks during joint deformation. In addition, the effect of joint roughness is analyzed by performing numerical compression tests. We also investigate how confining pressure affects volumetric deformation leading to opening or closure of developed microcracks and permeability changes of samples with joints.

  15. Experimental determination of a LMFBR seismic equivalent core model

    Energy Technology Data Exchange (ETDEWEB)

    Buland, P.; Fegeant, O.; Fontaine, B.; Gantenbein, F.

    1995-12-31

    Seismic analysis of pool type LMFBR requires to perform a finite element calculation of the reactor. Because of fluid structure interaction and non-linearities due to the presence of gaps between subassemblies, it is impossible to include in the reactor vessel finite elements model the real behaviour of the core. It is therefore required to find a linear equivalent core model (LECM) which will give for the reactor vessel the same results. The design of the LECM is based on an experimental test program conducted with the core mock-up RAPSODIE on Vesuve shaking table located at CEA/Saclay center. The tests permitted to validate a linear equivalent model, which characteristics correspond to the modal parameters of the mock-up (masses, elevations, frequencies...). These characteristics were estimated in air and in water, for different level of excitation. They permitted to quantify the added mass ratio (about 15%) which is in a rather good agreement with the computation when the free surface effect is correctly taken into account. (authors). 2 refs., 5 figs., 1 photo.

  16. Structural Analysis of Cuban Typical Model of Telecommunication Self-Supporting Towers under Seismic Load

    Directory of Open Access Journals (Sweden)

    Patricia Martín Rodríguez

    2012-07-01

    Full Text Available Self-supporting lattice towers are slender structures with low damping and high flexibility. They are sensitive to dynamic loads such as wind and earthquake. In the West of Cuba, structures should be analyzed under extreme winds and seismic effects, which raised their frequency during 2010 year. Self-supporting towers do not have the same dynamic behavior as buildings under seismic loads. Their specific structure features are not developed at design seismic codes, for that reason it is necessary to study methods of seismic analysis for self-supporting towers. The methods selected in this research are Modal Analysis Method proposed by Cuban Seismic Code (NC-46:1999 and modal superposition lineal dynamic analysis named Time History. It was selected for the study two self-supporting towers designed in Cuba, Versalles Model (3-legged and Najasa Model (4-legged. Comparative analysis between both methods is realized with extreme values of internal forces at element towers.

  17. On the nature of the seismic ringing of the Moon. Analytical modeling

    Science.gov (United States)

    Burmin, V. Yu.; Miroshnikov, V. V.; Fatyanov, A. G.

    2016-07-01

    The paper presents an analytical method for modeling of seismic wave fields at long distances. The method has no restrictions on the calculation accuracy, model of a medium and distance observations. It allows calculating the wave fields for large space-time scales characteristic of lunar experimental data. The most characteristic feature of the lunar seismograms is considerable duration of the seismic signal (seismic "ringing"). The seismic "ringing" on the Moon has been simulated based on the created program of calculation of wave fields.. Results of the simulation lead to the following conclusions. In a first approximation, a significant duration of the seismic "ringing" on the Moon can be explained by the resonance properties of a thin layer (regolith), without attracting the scattering effects due to the high degree of heterogeneity of the environment.

  18. Seismic analysis of the APR1400 nuclear reactor system using a verified beam element model

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong-beom [Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of); Park, No-Cheol, E-mail: pnch@yonsei.ac.kr [Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of); Lee, Sang-Jeong; Park, Young-Pil [Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of); Choi, Youngin [Korea Institute of Nuclear Safety, 62 Gwahak-ro, Yuseong-gu, Daejeon 34142 (Korea, Republic of)

    2017-03-15

    Highlights: • A simplified beam element model is constructed based on the real dynamic characteristics of the APR1400. • Time history analysis is performed to calculate the seismic responses of the structures. • Large deformations can be observed at the in-phase mode of reactor vessel and core support barrel. - Abstract: Structural integrity is the first priority in the design of nuclear reactor internal structures. In particular, nuclear reactor internals should be designed to endure external forces, such as those due to earthquakes. Many researchers have performed finite element analyses to meet these design requirements. Generally, a seismic analysis model should reflect the dynamic characteristics of the target system. However, seismic analysis based on the finite element method requires long computation times as well as huge storage space. In this research, a beam element model was developed and confirmed based on the real dynamic characteristics of an advanced pressurized water nuclear reactor 1400 (APR1400) system. That verification process enhances the accuracy of the finite element analysis using the beam elements, remarkably. Also, the beam element model reduces seismic analysis costs. Therefore, the beam element model was used to perform the seismic analysis. Then, the safety of the APR1400 was assessed based on a seismic analysis of the time history responses of its structures. Thus, efficient, accurate seismic analysis was demonstrated using the proposed beam element model.

  19. VS30 mapping and soil classification for seismic site effect evaluation in Dinar region, SW Turkey

    Science.gov (United States)

    Ismet Kanlı, Ali; Tildy, Péter; Prónay, Zsolt; Pınar, Ali; Hermann, László

    2006-04-01

    The Dinar earthquake (MS= 6.1) of 1995 October 1 killed 90 people and destroyed more than 4000 buildings. Despite the moderate size of the earthquake, the level of damage was extremely high, which led to many studies that were carried out in the region. The majority of these studies concluded that the main reasons for the damage were the construction errors and the poor soil conditions. However, at that time no appropriate soil condition map based on extended, high density measurements was available. Shear wave velocity is an important parameter for evaluating the dynamic behaviour of soil in the shallow subsurface. Thus site characterization in calculating seismic hazards is usually based on the near surface shear wave velocity values. The average shear wave velocity for the top 30 m of soil is referred to as VS30. For earthquake engineering design purposes, both the Uniform Building Code (UBC) and Eurocode 8 (EC8) codes use VS30 to classify sites according to the soil type. The Vs30 values calculated by using multichannel analysis of surface waves (MASW) were used to create a new soil classification map of the Dinar region. Surface seismic measurements were carried out at 50 locations mostly in Dinar city and its surroundings. The dispersion data of the recorded Rayleigh waves were inverted using a Genetic Algorithm (GA) method to obtain shear wave velocity profiles of the investigated sites. Thus the derived Vs30 map of the Dinar region was transformed to the UBC and EC8 standards. Soil classification results show that most parts of the region, located in alluvial basin, have low shear wave velocity values. These values are within the range of 160-240 m s-1 and thus fall into the SD and SE categories according to the UBC and the C and D categories according to EC8. Within the region, some parts located on the hill zone and the transition zone have better soil conditions [corresponding to SC (UBC) and B (EC8) categories] and have comparatively high shear wave

  20. Regional variation of inner core anisotropy from seismic normal mode observations.

    Science.gov (United States)

    Deuss, Arwen; Irving, Jessica C E; Woodhouse, John H

    2010-05-21

    Earth's solid inner core is surrounded by a convecting liquid outer core, creating the geodynamo driving the planet's magnetic field. Seismic studies using compressional body waves suggest hemispherical variation in the anisotropic structure of the inner core, but are poorly constrained because of limited earthquake and receiver distribution. Here, using normal mode splitting function measurements from large earthquakes, based on extended cross-coupling theory, we observe both regional variations and eastern versus western hemispherical anisotropy in the inner core. The similarity of this pattern with Earth's magnetic field suggests freezing-in of crystal alignment during solidification or texturing by Maxwell stress as origins of the anisotropy. These observations limit the amount of inner core super rotation, but would be consistent with oscillation.

  1. Application of consequence-based design criteria in regions of moderate seismicity

    Institute of Scientific and Technical Information of China (English)

    胡聿贤

    2003-01-01

    Current design criteria and principles of earthquake engineering design are reviewed, including safety factors, probabilistic approach, and two-level and multi-level functional design ideas. The modern multi-functional idea is discussed in greater details. When designing a structure, its resistance to and the intensity of the earthquake action are considered. The consequence of failure of the structure is considered only through a rough and empirical factor of importance, ranging usually from 1.0 to 1.5. This paper suggests a method of "consequence-based design," which considers the consequences of malfunctioning instead of simply an importance factor. The main argument for this method is that damage to a structure located in different types of societies may have very different consequences, which are dependant on its value and usefulness to the society and the seismicity in the region.

  2. Quantifying Regional Body Wave Attenuation in a Seismic Prone Zone of Northeast India

    Science.gov (United States)

    Bora, Nilutpal; Biswas, Rajib

    2017-03-01

    We evaluated the body wave attenuation parameter in Kopili region of northeast India. Using the modified algorithm of coda normalization method, we delineated frequency-dependent attenuation for both P and S waves. Taking more than 300 seismograms as input, we comprehensively studied microearthquake spectra in the frequency range of 1.5-12 Hz. The estimated values of {Q}_{P}^{-1} and {Q}_{S}^{-1} show strong frequency dependence. Based on this, we formulated empirical relationships corresponding to {Q}_{P}^{-1} and {Q}_{S}^{-1} for the study region. The relationships emerge to be {Q}_{P}^{-1} = ( {23.8 ± 6} ) × 10^{-3} {f}^{{( {-1.2 ± 0.008} )}} and {Q}_{S}^{-1} = ( {10.2 ± 2} ) × 10^{-3} {f}^{{( {-1.3 ± 0.02} )}} , respectively. The ratio {Q}_{P}^{-1} /{Q}_{S}^{-1} is found to be larger than unity for the entire frequency band which implies profound seismic activity and macroscale heterogeneity prevailing in the region. The study may act as the building block towards determination of source parameter and hazard-related studies in the region.

  3. Seismic tomography of Yunnan region using short-period surface wave phase velocity

    Institute of Scientific and Technical Information of China (English)

    何正勤; 苏伟; 叶太兰

    2004-01-01

    The data of short-period (1~18 s) surface waves recorded by 23 stations belonging to the digital seismic network of Yunnan Province of China are used in this paper. From these data, the dispersion curves of phase velocities of the fundamental mode Rayleigh wave along 209 paths are determined by using the two-station narrowband filtering cross-correlation method.Adopting tomography method, the distribution maps of phase velocities at various periods in Yunnan region are inverted. The maps of phase velocities on profiles along 24°N, 25°N, 26°N, 27°N and 100.5°E and the distribution maps of phase velocities at 3 periods in the study region are given. The results show that the phase velocity distribution in Yunnan region has strong variations in horizontal direction, and the phase velocity distribution in short-period range is closely related to the thickness of sedimentary layers in the shallow crust. The phase velocity in southern part of the Sichuan-Yunnan rhombic block encircled by the Honghe fault and Xiaojiang fault is obviously lower than that in surrounding areas. The epicentral locations of strong earthquakes in Yunnan region are mainly distributed in transitional zones between low and high phase velocities.

  4. Searchlight Correlation Detectors: Optimal Seismic Monitoring Using Regional and Global Networks

    Science.gov (United States)

    Gibbons, Steven J.; Kværna, Tormod; Näsholm, Sven Peter

    2015-04-01

    The sensitivity of correlation detectors increases greatly when the outputs from multiple seismic traces are considered. For single-array monitoring, a zero-offset stack of individual correlation traces will provide significant noise suppression and enhanced sensitivity for a source region surrounding the hypocenter of the master event. The extent of this region is limited only by the decrease in waveform similarity with increasing hypocenter separation. When a regional or global network of arrays and/or 3-component stations is employed, the zero-offset approach is only optimal when the master and detected events are co-located exactly. In many monitoring situations, including nuclear test sites and geothermal fields, events may be separated by up to many hundreds of meters while still retaining sufficient waveform similarity for correlation detection on single channels. However, the traveltime differences resulting from the hypocenter separation may result in significant beam loss on the zero-offset stack and a deployment of many beams for different hypothetical source locations in geographical space is required. The beam deployment necessary for optimal performance of the correlation detectors is determined by an empirical network response function which is most easily evaluated using the auto-correlation functions of the waveform templates from the master event. The correlation detector beam deployments for providing optimal network sensitivity for the North Korea nuclear test site are demonstrated for both regional and teleseismic monitoring configurations.

  5. Improving Seismic Velocity Models with Constraints from Autocorrelation of Ambient Seismic Noise and Signal

    Science.gov (United States)

    2016-03-24

    detector revisited: An improved strategy for signal detection at seismic and infrasound arrays, Bull. Seism . Soc. Am., 99, pp. 449-453, doi: 10.1785... Seism . Soc. of Am., 100, No. 2, pp. 606-617, doi: 10.1785/0120090120. Approved for public release; distribution is unlimited. 58 Larkin, S. P., A...Retrieval of the Green’s Function from Cross Correlation: The Canonical Elastic Problem, Bull. Seism . Soc. Am., 96, pp. 1182-1191. Schulte-Pelkum, V

  6. Modelling Active Faults in Probabilistic Seismic Hazard Analysis (PSHA) with OpenQuake: Definition, Design and Experience

    Science.gov (United States)

    Weatherill, Graeme; Garcia, Julio; Poggi, Valerio; Chen, Yen-Shin; Pagani, Marco

    2016-04-01

    The Global Earthquake Model (GEM) has, since its inception in 2009, made many contributions to the practice of seismic hazard modeling in different regions of the globe. The OpenQuake-engine (hereafter referred to simply as OpenQuake), GEM's open-source software for calculation of earthquake hazard and risk, has found application in many countries, spanning a diversity of tectonic environments. GEM itself has produced a database of national and regional seismic hazard models, harmonizing into OpenQuake's own definition the varied seismogenic sources found therein. The characterization of active faults in probabilistic seismic hazard analysis (PSHA) is at the centre of this process, motivating many of the developments in OpenQuake and presenting hazard modellers with the challenge of reconciling seismological, geological and geodetic information for the different regions of the world. Faced with these challenges, and from the experience gained in the process of harmonizing existing models of seismic hazard, four critical issues are addressed. The challenge GEM has faced in the development of software is how to define a representation of an active fault (both in terms of geometry and earthquake behaviour) that is sufficiently flexible to adapt to different tectonic conditions and levels of data completeness. By exploring the different fault typologies supported by OpenQuake we illustrate how seismic hazard calculations can, and do, take into account complexities such as geometrical irregularity of faults in the prediction of ground motion, highlighting some of the potential pitfalls and inconsistencies that can arise. This exploration leads to the second main challenge in active fault modeling, what elements of the fault source model impact most upon the hazard at a site, and when does this matter? Through a series of sensitivity studies we show how different configurations of fault geometry, and the corresponding characterisation of near-fault phenomena (including

  7. Geological Features Inferred from Local Seismic Tomography in the Sunda Strait and West Java regions, Indonesia

    Science.gov (United States)

    Nugraha, A. D.; Sakti, A. P.; Rohadi, S.; Widiyantoro, S.

    2012-12-01

    We have conducted seismic tomographic inversions to obtain a P-wave seismic velocity structure beneath the Sunda Strait and West Java regions, Indonesia. The Sunda Strait is located in a complex geological system i.e. in the transition from the oblique subduction beneath Sumatra to the nearly perpendicular subduction below Java. The Krakatau active volcano is located in the Sunda Strait. In this study, we have used selected P-wave arrival times from the data catalogs of the SeisComP-BMKG network (from 2009 to 2011) and the BMKG BALAI II network (from 1992 to 2011) compiled by Badan Meteorologi,Klimatologi dan Geofisika (BMKG), Indonesia. In total, there are 1,598 local earthquakes and 10,366 P-wave phases from 25 seismographic stations that have been used for the tomographic inversions. We have also relocated the hypocenter locations along with velocity inversions simultaneously. Our preliminary results depict some prominent geological features that include: (1) a low velocity anomaly beneath north of the Ujung Kulon region, which coincides with a low gravity anomaly resulting from a previous study, (2) a low velocity anomaly alignment beneath the Krakatau volcano in the Sunda Strait, (3) a sharp contrast in velocity anomalies extending from Pelabuhan Ratu towards Jakarta with a strike of SW-NE, and (4) a low velocity anomaly in the offshore of Pelabuhan Ratu that may be correlated with the continuation of the Cimandiri fault zone. More detailed information will be presented during the meeting. Keywords: tomography, Sunda Strait, West Java, velocity anomaly

  8. Spectral-Element Seismic Wave Propagation Codes for both Forward Modeling in Complex Media and Adjoint Tomography

    Science.gov (United States)

    Smith, J. A.; Peter, D. B.; Tromp, J.; Komatitsch, D.; Lefebvre, M. P.

    2015-12-01

    We present both SPECFEM3D_Cartesian and SPECFEM3D_GLOBE open-source codes, representing high-performance numerical wave solvers simulating seismic wave propagation for local-, regional-, and global-scale application. These codes are suitable for both forward propagation in complex media and tomographic imaging. Both solvers compute highly accurate seismic wave fields using the continuous Galerkin spectral-element method on unstructured meshes. Lateral variations in compressional- and shear-wave speeds, density, as well as 3D attenuation Q models, topography and fluid-solid coupling are all readily included in both codes. For global simulations, effects due to rotation, ellipticity, the oceans, 3D crustal models, and self-gravitation are additionally included. Both packages provide forward and adjoint functionality suitable for adjoint tomography on high-performance computing architectures. We highlight the most recent release of the global version which includes improved performance, simultaneous MPI runs, OpenCL and CUDA support via an automatic source-to-source transformation library (BOAST), parallel I/O readers and writers for databases using ADIOS and seismograms using the recently developed Adaptable Seismic Data Format (ASDF) with built-in provenance. This makes our spectral-element solvers current state-of-the-art, open-source community codes for high-performance seismic wave propagation on arbitrarily complex 3D models. Together with these solvers, we provide full-waveform inversion tools to image the Earth's interior at unprecedented resolution.

  9. Computational Software to Fit Seismic Data Using Epidemic-Type Aftershock Sequence Models and Modeling Performance Comparisons

    Science.gov (United States)

    Chu, A.

    2016-12-01

    Modern earthquake catalogs are often analyzed using spatial-temporal point process models such as the epidemic-type aftershock sequence (ETAS) models of Ogata (1998). My work implements three of the homogeneous ETAS models described in Ogata (1998). With a model's log-likelihood function, my software finds the Maximum-Likelihood Estimates (MLEs) of the model's parameters to estimate the homogeneous background rate and the temporal and spatial parameters that govern triggering effects. EM-algorithm is employed for its advantages of stability and robustness (Veen and Schoenberg, 2008). My work also presents comparisons among the three models in robustness, convergence speed, and implementations from theory to computing practice. Up-to-date regional seismic data of seismic active areas such as Southern California and Japan are used to demonstrate the comparisons. Data analysis has been done using computer languages Java and R. Java has the advantages of being strong-typed and easiness of controlling memory resources, while R has the advantages of having numerous available functions in statistical computing. Comparisons are also made between the two programming languages in convergence and stability, computational speed, and easiness of implementation. Issues that may affect convergence such as spatial shapes are discussed.

  10. Crustal structure of the Trans-European suture zone region along POLONAISE'97 seismic profile P4

    Science.gov (United States)

    Grad, Marek; Jensen, Susanne L.; Keller, G. Randy; Guterch, Aleksander; Thybo, Hans; Janik, Tomasz; Tiira, Timo; Yliniemi, Jukka; Luosto, Urmas; Motuza, Gediminas; Nasedkin, Viktor; Czuba, Wojciech; GaczyńSki, Edward; ŚRoda, Piotr; Miller, Kate C.; Wilde-Piórko, Monika; Komminaho, Kari; Jacyna, Juozas; Korabliova, Larisa

    2003-11-01

    The large-scale POLONAISE'97 seismic experiment investigated the velocity structure of the crust and upper mantle in the Trans-European suture zone (TESZ) region between the Precambrian east European craton (EEC) and Paleozoic platform that comprises terranes added during the Caledonian and Variscan orogenies (530-370 and 370-225 Ma, respectively). This experiment included 64 shots recorded by 613 seismic stations during two deployments. Very good quality data were recorded along five profiles, and the longest and most important one (P4) is the focus of this paper. Clear first arrivals and later phases of waves reflected/refracted in the crust and Moho were interpreted using two-dimensional (2-D) tomographic inversion and ray-tracing techniques. The crustal thickness along the profile varies from 30-35 km in the Paleozoic platform area to ˜40 km below and due northeast of the TESZ, to ˜43 km in the Polish part of the EEC, and to ˜50 km in Lithuania. The Paleozoic platform and EEC are divided by the Polish basin, so the upper crustal structure varies considerably. In the area of the Polish basin, the P wave velocity is very low (VP < 6.1 km/s) down to depths of 15-20 km, indicating that a very thick sedimentary sequence is present. We suggest two possible tectonic interpretations of the velocity models: (1) Baltica indented Avalonia, obducting its upper crust and underthrusting its lower crust in a tectonic flake structure and (2) a rifted margin of Baltica underlies the Polish basin. This model is similar to other interpretations of seismic profiles recorded in the Baltic Sea. The second model implies that the Paleozoic platform solely consists of Avalonian lithosphere and the EEC of Baltica lithosphere. It offers a simple explanation of the difference in crustal thickness of the two platforms. It also implies that the Caledonian and Variscan orogenies in this area were relatively "soft" collisions that left this continental margin largely intact.

  11. An asymptotic model of seismic reflection from a permeable layer

    Energy Technology Data Exchange (ETDEWEB)

    Silin, D.; Goloshubin, G.

    2009-10-15

    Analysis of compression wave propagation in a poroelastic medium predicts a peak of reflection from a high-permeability layer in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of Biot's model of poroelasticity. A review of the derivation of the main equations from the Hooke's law, momentum and mass balance equations, and Darcy's law suggests an alternative new physical interpretation of some coefficients of the classical poroelasticity. The velocity of wave propagation, the attenuation factor, and the wave number, are expressed in the form of power series with respect to a small dimensionless parameter. The absolute value of this parameter is equal to the product of the kinematic reservoir fluid mobility and the wave frequency. Retaining only the leading terms of the series leads to explicit and relatively simple expressions for the reflection and transmission coefficients for a planar wave crossing an interface between two permeable media, as well as wave reflection from a thin highly-permeable layer (a lens). Practical applications of the obtained asymptotic formulae are seismic modeling, inversion, and at-tribute analysis.

  12. Stochastic Modelling as a Tool for Seismic Signals Segmentation

    Directory of Open Access Journals (Sweden)

    Daniel Kucharczyk

    2016-01-01

    Full Text Available In order to model nonstationary real-world processes one can find appropriate theoretical model with properties following the analyzed data. However in this case many trajectories of the analyzed process are required. Alternatively, one can extract parts of the signal that have homogenous structure via segmentation. The proper segmentation can lead to extraction of important features of analyzed phenomena that cannot be described without the segmentation. There is no one universal method that can be applied for all of the phenomena; thus novel methods should be invented for specific cases. They might address specific character of the signal in different domains (time, frequency, time-frequency, etc.. In this paper we propose two novel segmentation methods that take under consideration the stochastic properties of the analyzed signals in time domain. Our research is motivated by the analysis of vibration signals acquired in an underground mine. In such signals we observe seismic events which appear after the mining activity, like blasting, provoked relaxation of rock, and some unexpected events, like natural rock burst. The proposed segmentation procedures allow for extraction of such parts of the analyzed signals which are related to mentioned events.

  13. Preparing a seismic hazard model for Switzerland: the view from PEGASOS Expert Group 3 (EG1c)

    Energy Technology Data Exchange (ETDEWEB)

    Musson, R. M. W. [British Geological Survey, West Mains Road, Edinburgh, EH9 3LA (United Kingdom); Sellami, S. [Swiss Seismological Service, ETH-Hoenggerberg, Zuerich (Switzerland); Bruestle, W. [Regierungspraesidium Freiburg, Abt. 9: Landesamt fuer Geologie, Rohstoffe und Bergbau, Ref. 98: Landeserdbebendienst, Freiburg im Breisgau (Germany)

    2009-05-15

    The seismic hazard model used in the PEGASOS project for assessing earth-quake hazard at four NPP sites was a composite of four sub-models, each produced by a team of three experts. In this paper, one of these models is described in detail by the authors. A criticism sometimes levelled at probabilistic seismic hazard studies is that the process by which seismic source zones are arrived at is obscure, subjective and inconsistent. Here, we attempt to recount the stages by which the model evolved, and the decisions made along the way. In particular, a macro-to-micro approach was used, in which three main stages can be described. The first was the characterisation of the overall kinematic model, the 'big picture' of regional seismo-genesis. Secondly, this was refined to a more detailed seismotectonic model. Lastly, this was used as the basis of individual sources, for which parameters can be assessed. Some basic questions had also to be answered about aspects of the approach to modelling to be used: for instance, is spatial smoothing an appropriate tool to apply? Should individual fault sources be modelled in an intra-plate environment? Also, the extent to which alternative modelling decisions should be expressed in a logic tree structure has to be considered. (author)

  14. Seismic hazard assessment for Myanmar: Earthquake model database, ground-motion scenarios, and probabilistic assessments

    Science.gov (United States)

    Chan, C. H.; Wang, Y.; Thant, M.; Maung Maung, P.; Sieh, K.

    2015-12-01

    We have constructed an earthquake and fault database, conducted a series of ground-shaking scenarios, and proposed seismic hazard maps for all of Myanmar and hazard curves for selected cities. Our earthquake database integrates the ISC, ISC-GEM and global ANSS Comprehensive Catalogues, and includes harmonized magnitude scales without duplicate events. Our active fault database includes active fault data from previous studies. Using the parameters from these updated databases (i.e., the Gutenberg-Richter relationship, slip rate, maximum magnitude and the elapse time of last events), we have determined the earthquake recurrence models of seismogenic sources. To evaluate the ground shaking behaviours in different tectonic regimes, we conducted a series of tests by matching the modelled ground motions to the felt intensities of earthquakes. Through the case of the 1975 Bagan earthquake, we determined that Atkinson and Moore's (2003) scenario using the ground motion prediction equations (GMPEs) fits the behaviours of the subduction events best. Also, the 2011 Tarlay and 2012 Thabeikkyin events suggested the GMPEs of Akkar and Cagnan (2010) fit crustal earthquakes best. We thus incorporated the best-fitting GMPEs and site conditions based on Vs30 (the average shear-velocity down to 30 m depth) from analysis of topographic slope and microtremor array measurements to assess seismic hazard. The hazard is highest in regions close to the Sagaing Fault and along the Western Coast of Myanmar as seismic sources there have earthquakes occur at short intervals and/or last events occurred a long time ago. The hazard curves for the cities of Bago, Mandalay, Sagaing, Taungoo and Yangon show higher hazards for sites close to an active fault or with a low Vs30, e.g., the downtown of Sagaing and Shwemawdaw Pagoda in Bago.

  15. Anatomy of a caldera: seismic velocity and attenuation models of the Campi Flegrei (Italy).

    Science.gov (United States)

    Calò, Marco; Tramelli, Anna

    2017-04-01

    Campi Flegrei is an active Caldera marked by strong vertical deformations of the soil called bradyseisms. The mechanisms proposed to explain this phenomenon are essentially three i) the presence of a shallow magmatic chamber that pushes the lid and consequently producing periodic variation of the soil level, ii) a thermic expansion of the geothermal aquifer due to the periodic increase of heat flux coming from a near magmatic chamber or deep fluids or iii) a combination of both phenomena. To solve the paradox, several models have been proposed to describe the nature and the geometry of the bodies responsible of the bradyseisms. Seismological tools allowed a rough description of the main features in terms of seismic velocities and attenuation parameters and till now were not able to resolve the smallest structures (<1.5-2km) located at shallow depth (0-4 km) and believed to be responsible of the soil deformations. Here we show Vp, Vp/Vs and Qp models carried out by applying an enhanced seismic tomography method combining the double difference approach (Zhang and Thurber, 2003) and the Weighted Average Method (Calò et al., 2009, Calò et al., 2011, 2013). The data used are the earthquakes recorded during the largest bradyseism crisis of the 80's. Our method allowed to image seismic velocity and attenuation structures with linear dimension of 0.5-1.2km, resulting in an improvement of the resolving power at least two times of the other published models (e.g. Priolo et al., 2012). The joint interpretation of seismic velocities and attenuation models allowed to discern small anomalous bodies at shallow depth (0.5-2.0 km) marked by relatively low Vp, high Vp/Vs ratio and low Qp values explainable with the presence of shallow geothermal water saturated reservoir from regions with low Vp, low Vp/Vs and low Qp possibly related to the gas saturated part of the reservoir. At deeper depth (2-3.5 km) bodies with high Vp and Vp/Vs and low Qp can be associated with magmatic

  16. 3D crustal seismic velocity model for the Gulf of Cadiz and adjacent areas (SW Iberia margin) based on seismic reflection and refraction profiles

    Science.gov (United States)

    Lozano, Lucía; Cantavella, Juan Vicente; Barco, Jaime; Carranza, Marta; Burforn, Elisa

    2016-04-01

    The Atlantic margin of the SW Iberian Peninsula and northern Morocco has been subject of study during the last 30 years. Many seismic reflection and refraction profiles have been carried out offshore, providing detailed information about the crustal structure of the main seafloor tectonic domains in the region, from the South Portuguese Zone and the Gulf of Cadiz to the Abyssal Plains and the Josephine Seamount. The interest to obtain a detailed and realistic velocity model for this area, integrating the available data from these studies, is clear, mainly to improve real-time earthquake hypocentral location and for tsunami and earthquake early warning. Since currently real-time seismic location tools allow the implementation of 3D velocity models, we aim to generate a full 3D crustal model. For this purpose we have reviewed more than 50 profiles obtained in different seismic surveys, from 1980 to 2008. Data from the most relevant and reliable 2D seismic velocity published profiles were retrieved. We first generated a Moho depth map of the studied area (latitude 32°N - 41°N and longitude 15°W - 5°W) by extracting Moho depths along each digitized profile with a 10 km spacing, and then interpolating this dataset using ordinary kriging method and generating the contour isodepth map. Then, a 3D crustal velocity model has been obtained. Selected vertical sections at different distances along each profile were considered to retrieve P-wave velocity values at each interface in order to reproduce the geometry and the velocity gradient within each layer. A double linear interpolation, both in distance and depth, with sampling rates of 10 km and 1 km respectively, was carried out to generate a (latitude, longitude, depth, velocity) matrix. This database of all the profiles was interpolated to obtain the P-wave velocity distribution map every kilometer of depth. The new 3D velocity model has been integrated in NonLinLoc location program to relocate several representative

  17. Seismic hazard assessment of Kashmir and Kangra valley region, Western Himalaya, India

    Directory of Open Access Journals (Sweden)

    Basab Mukhopadhyay

    2015-02-01

    Full Text Available A complete earthquake catalogue of the Western Himalaya (latitudes 30°N–36°N and longitudes 72°E–78°E for the period of 1501–2010 has been compiled with earthquake magnitude computed in moment magnitude (Mw scale. Pre- and early twentieth century records of earthquake damage have been documented from rare and out of print publications. Seismotectonics and seismic hazard for Kohistan arc, Kashmir–Hazara Syntaxis, Nanga-Parbat (Western Syntaxis, Karakoram and Himachal Himalaya are discussed with special reference to 1905 Kangra and 2005 Muzaffarabad earthquakes. Analyses of spatio-temporal variation in b-value from the region indicate significant precursor prior to the 2005 Muzaffarabad earthquake; progressive rise of background b-value observed and the main shock locates close to relative high b-value domains. Regions surrounding the location of the 1905 Kangra earthquake also display such high b-value for the period of 2005–2010 that calls for closer scrutiny. Temporal analysis of b-value from the epicentral block of Muzaffarabad earthquake clearly showed a high–low b-value couplet of 1.45–0.72, which may be treated as a typical precursor before an imminent large earthquake. Gumbel extreme value statistics indicate probability of occurrence of an event of Mw > 7.0 within 50 years in the region.

  18. The heterogeneous characteristics of crust-mantle structures and the seismic activities in the northwest Beijing region

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jin-ren; ZHANG Xian-kang; ZHANG Cheng-ke; ZHANG Jian-shi; LIU Bao-feng; REN Qing-fang; PAN Su-zhen; HAI Yan

    2005-01-01

    In this paper, the abnormal characteristics of the crustal structures in the seismic active region, Yanqing-Huailai and Zhangbei-Shangyi, are obtained by means of comprehensively interpreting and studying the data of deep seismic sounding profiles passing through the northwestern part of Zhangjiakou-Bohai seismic zone. The results show that the fluctuation of crystalline basement in the study region is obvious and that there exist considerable differences in depth in different geological units. The locally abrupt variation of crystalline basement depths may be regarded as a mark of existence of crystalline basement faults. These crystalline basement faults and deep crustal faults provide a pass for the magma upwelling, resulting in the strong inhomogeneity of crustal structures. These phenomena of the complex seismic reflected waves and locally discontinuous reflection zones with different energy indicate that the intensive squeeze and deformation of crust took place, which have led to the complex crustal structures and offered the dynamic source for the earthquake occurrence in this region. The low velocity bodies in different depths of crust and the local interface C1 in Zhangbei-Shangyi region may result from repeated magmatic activities. The certain stress accumulation in the brittle upper crust can cause the occurrence of earthquake under the action of local tectonic activity.

  19. Earthquake Rate Models for Evolving Induced Seismicity Hazard in the Central and Eastern US

    Science.gov (United States)

    Llenos, A. L.; Ellsworth, W. L.; Michael, A. J.

    2015-12-01

    Injection-induced earthquake rates can vary rapidly in space and time, which presents significant challenges to traditional probabilistic seismic hazard assessment methodologies that are based on a time-independent model of mainshock occurrence. To help society cope with rapidly evolving seismicity, the USGS is developing one-year hazard models for areas of induced seismicity in the central and eastern US to forecast the shaking due to all earthquakes, including aftershocks which are generally omitted from hazards assessments (Petersen et al., 2015). However, the spatial and temporal variability of the earthquake rates make them difficult to forecast even on time-scales as short as one year. An initial approach is to use the previous year's seismicity rate to forecast the next year's seismicity rate. However, in places such as northern Oklahoma the rates vary so rapidly over time that a simple linear extrapolation does not accurately forecast the future, even when the variability in the rates is modeled with simulations based on an Epidemic-Type Aftershock Sequence (ETAS) model (Ogata, JASA, 1988) to account for earthquake clustering. Instead of relying on a fixed time period for rate estimation, we explore another way to determine when the earthquake rate should be updated. This approach could also objectively identify new areas where the induced seismicity hazard model should be applied. We will estimate the background seismicity rate by optimizing a single set of ETAS aftershock triggering parameters across the most active induced seismicity zones -- Oklahoma, Guy-Greenbrier, the Raton Basin, and the Azle-Dallas-Fort Worth area -- with individual background rate parameters in each zone. The full seismicity rate, with uncertainties, can then be estimated using ETAS simulations and changes in rate can be detected by applying change point analysis in ETAS transformed time with methods already developed for Poisson processes.

  20. Subsurface geology of the Lusi region: preliminary results from a comprehensive seismic-stratigraphic study.

    Science.gov (United States)

    Moscariello, Andrea; Do Couto, Damien; Lupi, Matteo; Mazzini, Adriano

    2016-04-01

    We investigate the subsurface data of a large sector in the Sidoarjo district (East Java, Indonesia) where the sudden catastrophic Lusi eruption started the 26th May 2006. Our goal is to understand the stratigraphic and structural features which can be genetically related to the surface manifestations of deep hydrothermal fluids and thus allow us to predict possible future similar phenomena in the region. In the framework of the Lusi Lab project (ERC grant n° 308126) we examined a series of densely spaced 2D reflection commercial seismic lines This allowed the reconstruction of the lateral variability of key stratigraphic horizons as well as the main tectonic features. In particular, we shed light on the deep structure of the Watukosek fault system and the associated fracture corridors crossing the entire stratigraphic successions. To the South-West, when approaching the volcanic complex, we could identify a clear contrast in seismic facies between chaotic volcanoclastic wedges and clastic-prone sedimentary successions as well as between the deeper stratigraphic units consisting of carbonates and lateral shales units. The latter show possible ductile deformation associated to fault-controlled diapirism which control in turns deformation of overlying stratigraphic units and deep geo-fluids circulation. Large collapse structures recognized in the study area (e.g. well PRG-1) are interpreted as the results of shale movement at depth. Similarly to Lusi, vertical deformation zones ("pipes"), likely associated with deeply rooted strike-slip systems seem to be often located at the interface between harder carbonate rocks forming isolated build ups and the laterally nearby clastic (shale-prone)-units. The mechanisms of deformation of structural features (strike vs dip slip systems) which may affect either the basement rock or the overlying deeper stratigraphic rocks is also being investigated to understand the relationship between deep and shallower (i.e. meteoric) fluid

  1. The smart cluster method. Adaptive earthquake cluster identification and analysis in strong seismic regions

    Science.gov (United States)

    Schaefer, Andreas M.; Daniell, James E.; Wenzel, Friedemann

    2017-07-01

    Earthquake clustering is an essential part of almost any statistical analysis of spatial and temporal properties of seismic activity. The nature of earthquake clusters and subsequent declustering of earthquake catalogues plays a crucial role in determining the magnitude-dependent earthquake return period and its respective spatial variation for probabilistic seismic hazard assessment. This study introduces the Smart Cluster Method (SCM), a new methodology to identify earthquake clusters, which uses an adaptive point process for spatio-temporal cluster identification. It utilises the magnitude-dependent spatio-temporal earthquake density to adjust the search properties, subsequently analyses the identified clusters to determine directional variation and adjusts its search space with respect to directional properties. In the case of rapid subsequent ruptures like the 1992 Landers sequence or the 2010-2011 Darfield-Christchurch sequence, a reclassification procedure is applied to disassemble subsequent ruptures using near-field searches, nearest neighbour classification and temporal splitting. The method is capable of identifying and classifying earthquake clusters in space and time. It has been tested and validated using earthquake data from California and New Zealand. A total of more than 1500 clusters have been found in both regions since 1980 with M m i n = 2.0. Utilising the knowledge of cluster classification, the method has been adjusted to provide an earthquake declustering algorithm, which has been compared to existing methods. Its performance is comparable to established methodologies. The analysis of earthquake clustering statistics lead to various new and updated correlation functions, e.g. for ratios between mainshock and strongest aftershock and general aftershock activity metrics.

  2. The smart cluster method - Adaptive earthquake cluster identification and analysis in strong seismic regions

    Science.gov (United States)

    Schaefer, Andreas M.; Daniell, James E.; Wenzel, Friedemann

    2017-03-01

    Earthquake clustering is an essential part of almost any statistical analysis of spatial and temporal properties of seismic activity. The nature of earthquake clusters and subsequent declustering of earthquake catalogues plays a crucial role in determining the magnitude-dependent earthquake return period and its respective spatial variation for probabilistic seismic hazard assessment. This study introduces the Smart Cluster Method (SCM), a new methodology to identify earthquake clusters, which uses an adaptive point process for spatio-temporal cluster identification. It utilises the magnitude-dependent spatio-temporal earthquake density to adjust the search properties, subsequently analyses the identified clusters to determine directional variation and adjusts its search space with respect to directional properties. In the case of rapid subsequent ruptures like the 1992 Landers sequence or the 2010-2011 Darfield-Christchurch sequence, a reclassification procedure is applied to disassemble subsequent ruptures using near-field searches, nearest neighbour classification and temporal splitting. The method is capable of identifying and classifying earthquake clusters in space and time. It has been tested and validated using earthquake data from California and New Zealand. A total of more than 1500 clusters have been found in both regions since 1980 with M m i n = 2.0. Utilising the knowledge of cluster classification, the method has been adjusted to provide an earthquake declustering algorithm, which has been compared to existing methods. Its performance is comparable to established methodologies. The analysis of earthquake clustering statistics lead to various new and updated correlation functions, e.g. for ratios between mainshock and strongest aftershock and general aftershock activity metrics.

  3. Robust seismicity forecasting based on Bayesian parameter estimation for epidemiological spatio-temporal aftershock clustering models.

    Science.gov (United States)

    Ebrahimian, Hossein; Jalayer, Fatemeh

    2017-08-29

    In the immediate aftermath of a strong earthquake and in the presence of an ongoing aftershock sequence, scientific advisories in terms of seismicity forecasts play quite a crucial role in emergency decision-making and risk mitigation. Epidemic Type Aftershock Sequence (ETAS) models are frequently used for forecasting the spatio-temporal evolution of seismicity in the short-term. We propose robust forecasting of seismicity based on ETAS model, by exploiting the link between Bayesian inference and Markov Chain Monte Carlo Simulation. The methodology considers the uncertainty not only in the model parameters, conditioned on the available catalogue of events occurred before the forecasting interval, but also the uncertainty in the sequence of events that are going to happen during the forecasting interval. We demonstrate the methodology by retrospective early forecasting of seismicity associated with the 2016 Amatrice seismic sequence activities in central Italy. We provide robust spatio-temporal short-term seismicity forecasts with various time intervals in the first few days elapsed after each of the three main events within the sequence, which can predict the seismicity within plus/minus two standard deviations from the mean estimate within the few hours elapsed after the main event.

  4. A FINITE ELEMENT MODEL FOR SEISMICITY INDUCED BY FAULT INTERACTION

    Institute of Scientific and Technical Information of China (English)

    Chen Huaran; Li Yiqun; He Qiaoyun; Zhang Jieqing; Ma Hongsheng; Li Li

    2003-01-01

    On ths basis of interaction between faults, a finite element model for Southwest China is constructed, and the stress adjustment due to the strong earthquake occurrence in this region was studied. The preliminary results show that many strong earthquakes occurred in the area of increased stress in the model. Though the results are preliminary, the quasi-3D finite element model is meaningful for strong earthquake prediction.

  5. A FINITE ELEMENT MODEL FOR SEISMICITY INDUCED BY FAULT INTERACTION

    Institute of Scientific and Technical Information of China (English)

    ChenHuaran; LiYiqun; HeQiaoyun; ZhangJieqing; MaHongsheng; LiLi

    2003-01-01

    On ths basis of interaction between faults, a finite element model for Southwest China is constructed, and the stress adjustment due to the strong earthquake occurrence in this region was studied. The preliminary results show that many strong earthquakes occurred in the are a of increased stress in the model. Though the results are preliminary, the quasi-3D finite element model is meaningful for strong earthquake prediction.

  6. Discontinuum Modelling Approach for Stress Analysis at a Seismic Source: Case Study

    Science.gov (United States)

    Sainoki, Atsushi; Mitri, Hani S.; Yao, Mike; Chinnasane, Damodara

    2016-12-01

    Rockbursts in underground mines can cause devastating damage to mine workings; hence, it is important to be able to assess the potential for their occurrence. The present study focuses on a large seismic event that took place at an underground base metal mine in Canada. The event took place in a dyke near the 100/900 orebodies on 3880 Level (1180 m below surface) of the Copper Cliff Mine in Sudbury, Canada. A 3D continuum stress analysis of the orebodies, i.e., 100 and 900, using an orebody-wide model encompassing the major geological structures and in situ stress heterogeneity in the mine shows low potential for rockburst at the seismic source location—a result which contradicts the fact that a large seismic event actually took place. A postulation is thus made that there had been highly stressed regions caused by geological disturbances at the source location before mining activities took place. In order to verify the postulation, a further study is undertaken with the discrete element modelling technique, whereby a cube-shaped model containing a fracture network is subjected to a stress state similar to that at the source location. A model parametrical study is conducted with respect to the distribution of the fracture (joint) network and its mechanical properties. The results reveal that when joints are densely distributed at the source location, the stress state becomes significantly burst prone. It is observed that the length, density, stiffness, and orientation of joints have a large influence on the stress state along the joints, while the friction angle, cohesion, and tensile strength do not influence the stress state. A cube-shaped model is constructed with joint sets actually mapped at the mine and a stress analysis is performed. The results demonstrate the generation of highly stressed regions due to the interaction of the joints with the applied in situ stress fields, thus leading to burst-prone conditions. The present study numerically confirms that

  7. A post-seismic deformation model after the 2010 earthquakes in Latin America

    Science.gov (United States)

    Sánchez, Laura; Drewes, Hermann; Schmidt, Michael

    2015-04-01

    The Maule 2010 earthquake in Chile generated the largest displacements of geodetic observation stations ever observed in terrestrial reference systems. Coordinate changes came up to 4 meters, and deformations were measurable in distances up to more than 1000 km from the epicentre. The station velocities in the regions adjacent to the epicentre changed dramatically after the seism; while they were oriented eastward with approximately 2 cm/year before the event, they are now directed westward with about 1 cm/year. The 2010 Baja California earthquake in Mexico produced displacements in the decimetre level also followed by anomalous velocity changes. The main problem in geodetic applications is that there is no reliable reference system to be used practically in the region. For geophysical applications we have to redefine the tectonic structure in South America. The area south of 35° S … 40° S was considered as a stable part of the South American plate. Now we see that there are large and extended crustal deformations. The paper presents a new multi-year velocity model computed from the Geocentric Reference System of the Americas (SIRGAS) including only the four years after the seismic events (mid-2010 … mid-2014). These velocities are used to derive a continuous deformation model of the entire Latin American region from Mexico to Tierra de Fuego. The model is compared with the same velocity model for SIRGAS (VEMOS2009) before the earthquakes.

  8. Mapping seismic moment and b-value within the continental-collision orogenic-belt region of the Iranian Plateau

    Science.gov (United States)

    Mousavi, S. Mostafa

    2017-01-01

    In this paper, high-resolution map of the Gutenberg-Richter b-value and seismic moment-release are provided for the Iranian Plateau using the unified and homogeneous part of the seismicity record of the region (January 1995-July 2016). We use these parameters as stressmeters and qualitatively explore their correlations with the GPS velocity field, strain rate, faulting mechanism, attenuation, and structure of the region. Our goal is to reveal the correlations and anomalous patterns that can help to better understand the seismotectonics and the state of present-day crustal stress within the region. A negative correlation between b-value and seismic moment release as well as convergence rates is found. Correlation between geodetic measurements and seismic observations might indicate the existence of a strong mechanical coupling between the basement and the sediment cover across Zagros. High geodetic strain rates east of the Hormuz strait, southern central Alborz, and along the north Tabriz fault correspond to low b-value anomalies at these areas. A strong low b-value anomaly is observed at the major tectonic discontinuity between the Zagros continental collision and the oceanic Makran subduction.

  9. Resistivity and Seismic Surface Wave Tomography Results for the Nevşehir Kale Region: Cappadocia, Turkey

    Science.gov (United States)

    Coşkun, Nart; Çakır, Özcan; Erduran, Murat; Arif Kutlu, Yusuf

    2014-05-01

    The Nevşehir Kale region located in the middle of Cappadocia with approximately cone shape is investigated for existence of an underground city using the geophysical methods of electrical resistivity and seismic surface wave tomography together. Underground cities are generally known to exist in Cappadocia. The current study has obtained important clues that there may be another one under the Nevşehir Kale region. Two-dimensional resistivity and seismic profiles approximately 4-km long surrounding the Nevşehir Kale are measured to determine the distribution of electrical resistivities and seismic velocities under the profiles. Several high resistivity anomalies with a depth range 8-20 m are discovered to associate with a systematic void structure beneath the region. Because of the high resolution resistivity measurement system currently employed we were able to isolate the void structure from the embedding structure. Low seismic velocity zones associated with the high resistivity depths are also discovered. Using three-dimensional visualization techniques we show the extension of the void structure under the measured profiles.

  10. Seismicity pattern in north Sumatra–Great Nicobar region: In search of precursor for the 26 December 2004 earthquake

    Indian Academy of Sciences (India)

    Sujit Dasgupta; Basab Mukhopadhyay; Auditeya Bhattacharya

    2007-06-01

    We analyse the seismicity pattern including -value in the north Sumatra–Great Nicobar region from 1976 to 2004. The analysis suggests that there were a number of significant, intermediate and short-term precursors before the magnitude 7.6 earthquake of 2 November 2002. However, they were not found to be so prominent prior to the magnitude 9.0 earthquake of 26 December 2004 though downward migration of activity and a 50-day short-term quiescence was observed before the event. The various precursors identified include post-seismic and intermediate-term quiescence of 13 and 10 years respectively, between the 1976 (magnitude 6.3) and 2002 earthquakes with two years (1990–1991) of increase in background seismicity; renewed seismicity, downward migration of seismic activity and foreshocks in 2002, just before the mainshock. Spatial variation in -value with time indicates precursory changes in the form of high -value zone near the epicenter preceding the mainshocks of 2004 and 2002 and temporal rise in -value in the epicentral area before the 2002 earthquake.

  11. Seismic hazard estimation of northern Iran using smoothed seismicity

    Science.gov (United States)

    Khoshnevis, Naeem; Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Cramer, Chris H.

    2017-07-01

    This article presents a seismic hazard assessment for northern Iran, where a smoothed seismicity approach has been used in combination with an updated seismic catalog and a ground motion prediction equation recently found to yield good fit with data. We evaluate the hazard over a geographical area including the seismic zones of Azerbaijan, the Alborz Mountain Range, and Kopeh-Dagh, as well as parts of other neighboring seismic zones that fall within our region of interest. In the chosen approach, seismic events are not assigned to specific faults but assumed to be potential seismogenic sources distributed within regular grid cells. After performing the corresponding magnitude conversions, we decluster both historical and instrumental seismicity catalogs to obtain earthquake rates based on the number of events within each cell, and smooth the results to account for the uncertainty in the spatial distribution of future earthquakes. Seismicity parameters are computed for each seismic zone separately, and for the entire region of interest as a single uniform seismotectonic region. In the analysis, we consider uncertainties in the ground motion prediction equation, the seismicity parameters, and combine the resulting models using a logic tree. The results are presented in terms of expected peak ground acceleration (PGA) maps and hazard curves at selected locations, considering exceedance probabilities of 2 and 10% in 50 years for rock site conditions. According to our results, the highest levels of hazard are observed west of the North Tabriz and east of the North Alborz faults, where expected PGA values are between about 0.5 and 1 g for 10 and 2% probability of exceedance in 50 years, respectively. We analyze our results in light of similar estimates available in the literature and offer our perspective on the differences observed. We find our results to be helpful in understanding seismic hazard for northern Iran, but recognize that additional efforts are necessary to

  12. Seismic hazard estimation of northern Iran using smoothed seismicity

    Science.gov (United States)

    Khoshnevis, Naeem; Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Cramer, Chris H.

    2017-03-01

    This article presents a seismic hazard assessment for northern Iran, where a smoothed seismicity approach has been used in combination with an updated seismic catalog and a ground motion prediction equation recently found to yield good fit with data. We evaluate the hazard over a geographical area including the seismic zones of Azerbaijan, the Alborz Mountain Range, and Kopeh-Dagh, as well as parts of other neighboring seismic zones that fall within our region of interest. In the chosen approach, seismic events are not assigned to specific faults but assumed to be potential seismogenic sources distributed within regular grid cells. After performing the corresponding magnitude conversions, we decluster both historical and instrumental seismicity catalogs to obtain earthquake rates based on the number of events within each cell, and smooth the results to account for the uncertainty in the spatial distribution of future earthquakes. Seismicity parameters are computed for each seismic zone separately, and for the entire region of interest as a single uniform seismotectonic region. In the analysis, we consider uncertainties in the ground motion prediction equation, the seismicity parameters, and combine the resulting models using a logic tree. The results are presented in terms of expected peak ground acceleration (PGA) maps and hazard curves at selected locations, considering exceedance probabilities of 2 and 10% in 50 years for rock site conditions. According to our results, the highest levels of hazard are observed west of the North Tabriz and east of the North Alborz faults, where expected PGA values are between about 0.5 and 1 g for 10 and 2% probability of exceedance in 50 years, respectively. We analyze our results in light of similar estimates available in the literature and offer our perspective on the differences observed. We find our results to be helpful in understanding seismic hazard for northern Iran, but recognize that additional efforts are necessary to

  13. Modelling the 2013 North Aegean (Greece) seismic sequence: geometrical and frictional constraints, and aftershock probabilities

    Science.gov (United States)

    Karakostas, Vassilis; Papadimitriou, Eleftheria; Gospodinov, Dragomir

    2014-04-01

    The 2013 January 8 Mw 5.8 North Aegean earthquake sequence took place on one of the ENE-WSW trending parallel dextral strike slip fault branches in this area, in the continuation of 1968 large (M = 7.5) rupture. The source mechanism of the main event indicates predominantly strike slip faulting in agreement with what is expected from regional seismotectonics. It was the largest event to have occurred in the area since the establishment of the Hellenic Unified Seismological Network (HUSN), with an adequate number of stations in close distances and full azimuthal coverage, thus providing the chance of an exhaustive analysis of its aftershock sequence. The main shock was followed by a handful of aftershocks with M ≥ 4.0 and tens with M ≥ 3.0. Relocation was performed by using the recordings from HUSN and a proper crustal model for the area, along with time corrections in each station relative to the model used. Investigation of the spatial and temporal behaviour of seismicity revealed possible triggering of adjacent fault segments. Theoretical static stress changes from the main shock give a preliminary explanation for the aftershock distribution aside from the main rupture. The off-fault seismicity is perfectly explained if μ > 0.5 and B = 0.0, evidencing high fault friction. In an attempt to forecast occurrence probabilities of the strong events (Mw ≥ 5.0), estimations were performed following the Restricted Epidemic Type Aftershock Sequence (RETAS) model. The identified best-fitting MOF model was used to execute 1-d forecasts for such aftershocks and follow the probability evolution in time during the sequence. Forecasting was also implemented on the base of a temporal model of aftershock occurrence, different from the modified Omori formula (the ETAS model), which resulted in probability gain (though small) in strong aftershock forecasting for the beginning of the sequence.

  14. Seismic analysis of a reinforced concrete containment vessel model

    Energy Technology Data Exchange (ETDEWEB)

    RANDY,JAMES J.; CHERRY,JEFFERY L.; RASHID,YUSEF R.; CHOKSHI,NILESH

    2000-02-03

    Pre-and post-test analytical predictions of the dynamic behavior of a 1:10 scale model Reinforced Concrete Containment Vessel are presented. This model, designed and constructed by the Nuclear Power Engineering Corp., was subjected to seismic simulation tests using the high-performance shaking table at the Tadotsu Engineering Laboratory in Japan. A group of tests representing design-level and beyond-design-level ground motions were first conducted to verify design safety margins. These were followed by a series of tests in which progressively larger base motions were applied until structural failure was induced. The analysis was performed by ANATECH Corp. and Sandia National Laboratories for the US Nuclear Regulatory Commission, employing state-of-the-art finite-element software specifically developed for concrete structures. Three-dimensional time-history analyses were performed, first as pre-test blind predictions to evaluate the general capabilities of the analytical methods, and second as post-test validation of the methods and interpretation of the test result. The input data consisted of acceleration time histories for the horizontal, vertical and rotational (rocking) components, as measured by accelerometers mounted on the structure's basemat. The response data consisted of acceleration and displacement records for various points on the structure, as well as time-history records of strain gages mounted on the reinforcement. This paper reports on work in progress and presents pre-test predictions and post-test comparisons to measured data for tests simulating maximum design basis and extreme design basis earthquakes. The pre-test analyses predict the failure earthquake of the test structure to have an energy level in the range of four to five times the energy level of the safe shutdown earthquake. The post-test calculations completed so far show good agreement with measured data.

  15. The Seismicity of the Central Apennines Region Studied by Means of a Physics-Based Earthquake Simulator

    Science.gov (United States)

    Console, R.; Vannoli, P.; Carluccio, R.

    2016-12-01

    The application of a physics-based earthquake simulation algorithm to the central Apennines region, where the 24 August 2016 Amatrice earthquake occurred, allowed the compilation of a synthetic seismic catalog lasting 100 ky, and containing more than 500,000 M ≥ 4.0 events, without the limitations that real catalogs suffer in terms of completeness, homogeneity and time duration. The algorithm on which this simulator is based is constrained by several physical elements as: (a) an average slip rate for every single fault in the investigated fault systems, (b) the process of rupture growth and termination, leading to a self-organized earthquake magnitude distribution, and (c) interaction between earthquake sources, including small magnitude events. Events nucleated in one fault are allowed to expand into neighboring faults, even belonging to a different fault system, if they are separated by less than a given maximum distance. The seismogenic model upon which we applied the simulator code, was derived from the DISS 3.2.0 database (http://diss.rm.ingv.it/diss/), selecting all the fault systems that are recognized in the central Apennines region, for a total of 24 fault systems. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which are comparable with those of real observations. These features include long-term periodicity and clustering of strong earthquakes, and a realistic earthquake magnitude distribution departing from the linear Gutenberg-Richter distribution in the moderate and higher magnitude range. The statistical distribution of earthquakes with M ≥ 6.0 on single faults exhibits a fairly clear pseudo-periodic behavior, with a coefficient of variation Cv of the order of 0.3-0.6. We found in our synthetic catalog a clear trend of long-term acceleration of seismic activity preceding M ≥ 6.0 earthquakes and quiescence following those earthquakes. Lastly, as an example of a

  16. Modeling and validation of a 3D velocity structure for the Santa Clara Valley, California, for seismic-wave simulations

    Science.gov (United States)

    Hartzell, S.; Harmsen, S.; Williams, R.A.; Carver, D.; Frankel, A.; Choy, G.; Liu, P.-C.; Jachens, R.C.; Brocher, T.M.; Wentworth, C.M.

    2006-01-01

    A 3D seismic velocity and attenuation model is developed for Santa Clara Valley, California, and its surrounding uplands to predict ground motions from scenario earthquakes. The model is developed using a variety of geologic and geophysical data. Our starting point is a 3D geologic model developed primarily from geologic mapping and gravity and magnetic surveys. An initial velocity model is constructed by using seismic velocities from boreholes, reflection/refraction lines, and spatial autocorrelation microtremor surveys. This model is further refined and the seismic attenuation is estimated through waveform modeling of weak motions from small local events and strong-ground motion from the 1989 Loma Prieta earthquake. Waveforms are calculated to an upper frequency of 1 Hz using a parallelized finite-difference code that utilizes two regions with a factor of 3 difference in grid spacing to reduce memory requirements. Cenozoic basins trap and strongly amplify ground motions. This effect is particularly strong in the Evergreen Basin on the northeastern side of the Santa Clara Valley, where the steeply dipping Silver Creek fault forms the southwestern boundary of the basin. In comparison, the Cupertino Basin on the southwestern side of the valley has a more moderate response, which is attributed to a greater age and velocity of the Cenozoic fill. Surface waves play a major role in the ground motion of sedimentary basins, and they are seen to strongly develop along the western margins of the Santa Clara Valley for our simulation of the Loma Prieta earthquake.

  17. Comparative seismic and petrographic crustal study between the Western and Eastern Sierras Pampeanas region (31°S

    Directory of Open Access Journals (Sweden)

    P. Alvarado

    2005-12-01

    Full Text Available The ancient Sierras Pampeanas in the central west part of Argentina are a seismically active region in the back-arc of the Andes. Their crystalline basement cored uplifts extend up to 800 km east of the oceanic trench over the flat subduction segment of the Nazca plate. Approximately 40 felt crustal earthquakes, are reported per year for this region. Historic and modern seismicity indicates that the Western Sierras Pampeanas (WSP have more crustal earthquakes of greater-size than the Eastern Sierras Pampeanas (ESP. Remarkable changes in composition and structure also characterize the WSP and ESP basements. We have quantitatively compared both regions using seismological constrains. A recent regional study of moderate earthquakes shows reverse and thrust focal mechanisms occurring at depths down to 25 km in the WSP. In contrast, the ESP have reverse and strike-slip focal mechanisms of shallower depths (< 10 km. A seismic velocity structure of Vp 6.4 km/s, Vp/Vs ~1.80, and thickness 50 km, best represents the WSP crust. The ESP crust is characterized by Vp 6.0 km/s, Vp/Vs < 1.70, and thickness 30 km. These seismological determinations correlate with the interpretation of a different origin for the western and eastern terranes. The WSP show seismic properties indicative of a more mafic-ultramafic thick crust consistent with an oceanic island-arc and back-arc formation. The ESP show crustal seismic properties consistent with a higher silica content and with a formation by the collision of a continental terrane.

  18. Seismic model of Mars. 2. Free oscillations and travel times

    Science.gov (United States)

    Gudkova, Tamara; Lognonne, Philippe; Raevskiy, Sergey; Zharkov, Vladimir

    When constructing an interior structure model of a planet, it is common used method to describe the model by a restricted set of parameters: the thickness of the crust, the location of phase transitions, the core radius. The variation of these parameters originates from the uncertainties in temperature profile, composition, elastic and anelastic properties of relevant minerals. Water content should also be considered as a compositional variable in the mantle. Olivine and its high pressure phases, wadsleyite and ringwoodite are particularly important as they constitute about 60 wt% of the Martian mantle and have probably large capacity for water in the Martian mantle (Zharkov and Gudkova, 2014). At present Mars’ internal density distribution is constrained by the recent estimates of the moment of inertia and the Love number k _{2} (Konoplive et al., 2011). Below we use the data from Earth studies and laboratory data (Mao et al., 2010, 2011, 2012,extrapolated for P-T conditions in Mars, and show how the admixture of water in the main Martian minerals influences velocity drops at phase transition boundaries in Martian interiors and study the effects of hydration on the periods of free oscillations and travel times for P, PcP, S, ScS waves , which could serve as additional constraints, if upcoming seismic experiments are successful, as they can potentially constrain mantle composition and make more precise the location of transition zones. It is of importance to determine the depth of the phase transitions in the mantle, as it will fix the temperature profile in Mars. Our analysis is based on a trial seismic model M14_3 from (Zharkov et al., 2009). The crust is 50 km thick (with density of 2.9 g/cm (3) ), the molar ratio Fe/(Fe+Mg) in the mantle is 0.20, the Fe-Ni core contains 70 mol % H in addition to 14 wt % S with radius of 1800 km. The bulk Fe/Si ratio is close to chondritic 1.7. The upper mantle extends down to 1590 km depth. Olivine-wadsleite transition zone

  19. Seismic facies; Facies sismicas

    Energy Technology Data Exchange (ETDEWEB)

    Johann, Paulo Roberto Schroeder [PETROBRAS, Rio de Janeiro, RJ (Brazil). Exploracao e Producao Corporativo. Gerencia de Reservas e Reservatorios]. E-mail: johann@petrobras.com.br

    2004-11-01

    The method presented herein describes the seismic facies as representations of curves and vertical matrixes of the lithotypes proportions. The seismic facies are greatly interested in capturing the spatial distributions (3D) of regionalized variables, as for example, lithotypes, sedimentary facies groups and/ or porosity and/or other properties of the reservoirs and integrate them into the 3D geological modeling (Johann, 1997). Thus when interpreted as curves or vertical matrixes of proportions, seismic facies allow us to build a very important tool for structural analysis of regionalized variables. The matrixes have an important application in geostatistical modeling. In addition, this approach provides results about the depth and scale of the wells profiles, that is, seismic data is integrated to the characterization of reservoirs in depth maps and in high resolution maps. The link between the different necessary technical phases involved in the classification of the segments of seismic traces is described herein in groups of predefined traces of two approaches: a) not supervised and b) supervised by the geological knowledge available on the studied reservoir. The multivariate statistical methods used to obtain the maps of the seismic facies units are interesting tools to be used to provide a lithostratigraphic and petrophysical understanding of a petroleum reservoir. In the case studied these seismic facies units are interpreted as representative of the depositional system as a part of the Namorado Turbiditic System, Namorado Field, Campos Basin.Within the scope of PRAVAP 19 (Programa Estrategico de Recuperacao Avancada de Petroleo - Strategic Program of Advanced Petroleum Recovery) some research work on algorithms is underway to select new optimized attributes to apply seismic facies. One example is the extraction of attributes based on the wavelet transformation and on the time-frequency analysis methodology. PRAVAP is also carrying out research work on an

  20. Assessing Induced Seismicity Models for Use in Deep Geothermal Energy Projects

    Science.gov (United States)

    Király, E.; Zechar, J. D.; Gischig, V.; Karvounis, D.; Wiemer, S.

    2014-12-01

    The decision to phase out nuclear power in Switzerland by 2034 accelerated research on deep geothermal energy, which has the ability to contribute to long-term energy resources. Induced seismicty is a nessesary tool to create an enhanced geothermal system; however, potential seismic hazard poses a major challange to the widespread implementation of this technology. Monitoring and controlling induced seismicity with warning systems requires models that are updated as new data arrive and that are cast in probabilistic terms. Our main question is: is it possible to forecast the seismic response of the geothermal site during and after stimulation with models based on observed seismicity and hydraulic data? To answer the question, we explore the predictive performance of various stochastic and hybrid models. The goal is to find the most suitable model or model combination for forecasting induced microseismicity and unexpected events in geothermal reservoirs.In this study, we consider the Basel 2006 dataset and generate forecasts of the number and spatial distribution of seismicity in the next six hours. We explore two models: (1) a hydro-geomechanical stochastic seed model based on pore pressure diffusion with irreversible permeability enhancement; and (2) four variants of a 3D "Shapiro" model which combine estimates of seismogenic index with a spatial forecast based on kernel-smoothed seismicity and temporal weighting. For both models, hydraulic and seismic parameters are calibrated against data from a learning period (starting at the beginning of injection) every six hours. We assess the models using metrics developed by the Collaboratory for the Study of Earthquake Predictability: we check the overall consistency of forecasts with the observations by comparing the number, magnitude and spatial distribution of forecast events with the observed induced earthquakes. We also compare the models with each other in terms of information gain, allowing pairwise ranking.

  1. Development of Simplified Probabilistic Risk Assessment Model for Seismic Initiating Event

    Energy Technology Data Exchange (ETDEWEB)

    S. Khericha; R. Buell; S. Sancaktar; M. Gonzalez; F. Ferrante

    2012-06-01

    ABSTRACT This paper discusses a simplified method to evaluate seismic risk using a methodology built on dividing the seismic intensity spectrum into multiple discrete bins. The seismic probabilistic risk assessment model uses Nuclear Regulatory Commission’s (NRC’s) full power Standardized Plant Analysis Risk (SPAR) model as the starting point for development. The seismic PRA models are integrated with their respective internal events at-power SPAR model. This is accomplished by combining the modified system fault trees from the full power SPAR model with seismic event tree logic. The peak ground acceleration is divided into five bins. The g-value for each bin is estimated using the geometric mean of lower and upper values of that particular bin and the associated frequency for each bin is estimated by taking the difference between upper and lower values of that bin. The component’s fragilities are calculated for each bin using the plant data, if available, or generic values of median peak ground acceleration and uncertainty values for the components. For human reliability analysis (HRA), the SPAR HRA (SPAR-H) method is used which requires the analysts to complete relatively straight forward worksheets that include the performance shaping factors (PSFs). The results are then used to estimate human error probabilities (HEPs) of interest. This work is expected to improve the NRC’s ability to include seismic hazards in risk assessments for operational events in support of the reactor oversight program (e.g., significance determination process).

  2. Regional geothermal 3D modelling in Denmark

    Science.gov (United States)

    Poulsen, S. E.; Balling, N.; Bording, T. S.; Nielsen, S. B.

    2012-04-01

    In the pursuit of sustainable and low carbon emission energy sources, increased global attention has been given to the exploration and exploitation of geothermal resources within recent decades. In 2009 a national multi-disciplinary geothermal research project was established. As a significant part of this project, 3D temperature modelling is to be carried out, with special emphasis on temperatures of potential geothermal reservoirs in the Danish area. The Danish subsurface encompasses low enthalpy geothermal reservoirs of mainly Triassic and Jurassic age. Geothermal plants at Amager (Copenhagen) and Thisted (Northern Jutland) have the capacity of supplying the district heating network with up to 14 MW and 7 MW, respectively, by withdrawing warm pore water from the Gassum (Lower Jurassic/Upper Triassic) and Bunter (Lower Triassic) sandstone reservoirs, respectively. Explorative studies of the subsurface temperature regime typically are based on a combination of observations and modelling. In this study, the open-source groundwater modelling code MODFLOW is modified to simulate the subsurface temperature distribution in three dimensions by taking advantage of the mathematical similarity between saturated groundwater flow (Darcy flow) and heat conduction. A numerical model of the subsurface geology in Denmark is built and parameterized from lithological information derived from joint interpretation of seismic surveys and borehole information. Boundary conditions are constructed from knowledge about the heat flow from the Earth's interior and the shallow ground temperature. Matrix thermal conductivities have been estimated from analysis of high-resolution temperature logs measured in deep wells and porosity-depth relations are included using interpreted main lithologies. The model takes into account the dependency of temperature and pressure on thermal conductivity. Moreover, a transient model based correction of the paleoclimatic thermal disturbance caused by the

  3. Long-Term Seismicity Behavior of the Zagros Region in Iran

    Science.gov (United States)

    Madahizadeh, Rohollah; Mostafazadeh, Mehrdad; Ansari, Anooshiravan

    2016-08-01

    To achieve a comprehensive attitude about seismicity, it is necessary to consider spatial and magnitude distributions of earthquakes. Earthquake distributions in space and magnitude can be quantified by means of spatial fractal dimension D( s) and Gutenberg-Richter b value. In this paper, b value and D( s) are used to evaluate seismicity of the Zagros zone (Iran) in time interval 1964 to 2012. Seismic catalog of the Zagros zone is extracted from unified seismic catalog of the Iranian Plateau. The b value and D( s) are estimated using frequency-magnitude distribution, Kijko-Sellevoll (Bull Seism Soc Am 79(3):645-654, 1989) and correlation integral methods. Correlations between spatial variations in b value and D( s) along individual profiles across the North Zagros and the Central Zagros indicate different stress release regimes for North and Central parts of the Zagros zone. Evaluation of b value with respect to depth along the profiles indicates larger b values at shallower depths. Temporal variations in b value and D( s) are also obtained from background seismicity to evaluate seismicity behavior of the Zagros zone. Our results indicate high b values and moderate D( s) for seismicity of the North Zagros, while seismicity of the Central Zagros has low b values and high D( s) during time interval 1964-2012. Asperities of the Main Zagros Thrust are also located by investigating ratio D( s)/ b along the Main Zagros Thrust.

  4. A model for the magmatic-hydrothermal system at Mount Rainier, Washington, from seismic and geochemical observations

    Science.gov (United States)

    Moran, S. C.; Zimbelman, D. R.; Malone, S. D.

    Mount Rainier is one of the most seismically active volcanoes in the Cascade Range, with an average of one to two high-frequency volcano-tectonic (or VT) earthquakes occurring directly beneath the summit in a given month. Despite this level of seismicity, little is known about its cause. The VT earthquakes occur at a steady rate in several clusters below the inferred base of the Quaternary volcanic edifice. More than half of 18 focal mechanisms determined for these events are normal, and most stress axes deviate significantly from the regional stress field. We argue that these characteristics are most consistent with earthquakes in response to processes associated with circulation of fluids and magmatic gases within and below the base of the edifice.Circulation of these fluids and gases has weakened rock and reduced effective stress to the point that gravity-induced brittle fracture, due to the weight of the overlying edifice, can occur. Results from seismic tomography and rock, water, and gas geochemistry studies support this interpretation. We combine constraints from these studies into a model for the magmatic system that includes a large volume of hot rock (temperatures greater than the brittle-ductile transition) with small pockets of melt and/or hot fluids at depths of 8-18km below the summit. We infer that fluids and heat from this volume reach the edifice via a narrow conduit, resulting in fumarolic activity at the summit, hydrothermal alteration of the edifice, and seismicity.

  5. Global Seismic Hazard Assessment Program - GSHAP legacy

    Directory of Open Access Journals (Sweden)

    Laurentiu Danciu

    2015-04-01

    Full Text Available Global Seismic Hazard Assessment Program - or simply GSHAP, when launched, almost two decades ago, aimed at establishing a common framework to evaluate the seismic hazard over geographical large-scales, i.e. countries, regions, continents and finally the globe. Its main product, the global seismic hazard map was a milestone, unique at that time and for a decade have served as the main reference worldwide. Today, for most of the Earth’s seismically active regions such Europe, Northern and Southern America, Central and South-East Asia, Japan, Australia, New Zealand, the GSHAP seismic hazard map is outdated. The rapid increase of the new data, advance on the earthquake process knowledge, technological progress, both hardware and software, contributed all in updates of the seismic hazard models. We present herein, a short retrospective overview of the achievements as well as the pitfalls of the GSHAP. Further, we describe the next generation of seismic hazard models, as elaborated within the Global Earthquake Model, regional programs: the 2013 European Seismic Hazard Model, the 2014 Earthquake Model for Middle East, and the 2015 Earthquake Model of Central Asia. Later, the main characteristics of these regional models are summarized and the new datasets fully harmonized across national borders are illustrated for the first time after the GSHAP completion.

  6. Procedures for computing site seismicity

    Science.gov (United States)

    Ferritto, John

    1994-02-01

    This report was prepared as part of the Navy's Seismic Hazard Mitigation Program. The Navy has numerous bases located in seismically active regions throughout the world. Safe effective design of waterfront structures requires determining expected earthquake ground motion. The Navy's problem is further complicated by the presence of soft saturated marginal soils that can significantly amplify the levels of seismic shaking as evidenced in the 1989 Loma Prieta earthquake. The Naval Facilities Engineering Command's seismic design manual, NAVFAC P355.l, requires a probabilistic assessment of ground motion for design of essential structures. This report presents the basis for the Navy's Seismic Hazard Analysis procedure that was developed and is intended to be used with the Seismic Hazard Analysis computer program and user's manual. This report also presents data on geology and seismology to establish the background for the seismic hazard model developed. The procedure uses the historical epicenter data base and available geologic data, together with source models, recurrence models, and attenuation relationships to compute the probability distribution of site acceleration and an appropriate spectra. This report discusses the developed stochastic model for seismic hazard evaluation and the associated research.

  7. The global short-period wavefield modelled with a Monte Carlo seismic phonon method

    Science.gov (United States)

    Shearer, Peter M.; Earle, Paul

    2004-01-01

    At high frequencies (∼1 Hz), much of the seismic energy arriving at teleseismic distances is not found in the main phases (e.g. P, PP, S, etc.) but is contained in the extended coda that follows these arrivals. This coda results from scattering off small-scale velocity and density perturbations within the crust and mantle and contains valuable information regarding the depth dependence and strength of this heterogeneity as well as the relative importance of intrinsic versus scattering attenuation. Most analyses of seismic coda to date have concentrated on S-wave coda generated from lithospheric scattering for events recorded at local and regional distances. Here, we examine the globally averaged vertical-component, 1-Hz wavefield (>10° range) for earthquakes recorded in the IRIS FARM archive from 1990 to 1999. We apply an envelope-function stacking technique to image the average time–distance behavior of the wavefield for both shallow (≤50 km) and deep (≥500 km) earthquakes. Unlike regional records, our images are dominated by P and P coda owing to the large effect of attenuation on PPand S at high frequencies. Modelling our results is complicated by the need to include a variety of ray paths, the likely contributions of multiple scattering and the possible importance of P-to-S and S-to-P scattering. We adopt a stochastic, particle-based approach in which millions of seismic phonons are randomly sprayed from the source and tracked through the Earth. Each phonon represents an energy packet that travels along the appropriate ray path until it is affected by a discontinuity or a scatterer. Discontinuities are modelled by treating the energy normalized reflection and transmission coefficients as probabilities. Scattering probabilities and scattering angles are computed in a similar fashion, assuming random velocity and density perturbations characterized by an exponential autocorrelation function. Intrinsic attenuation is included by reducing the energy

  8. The Sacred Mountain of Varallo in Italy: seismic risk assessment by acoustic emission and structural numerical models.

    Science.gov (United States)

    Carpinteri, Alberto; Lacidogna, Giuseppe; Invernizzi, Stefano; Accornero, Federico

    2013-01-01

    We examine an application of Acoustic Emission (AE) technique for a probabilistic analysis in time and space of earthquakes, in order to preserve the valuable Italian Renaissance Architectural Complex named "The Sacred Mountain of Varallo." Among the forty-five chapels of the Renaissance Complex, the structure of the Chapel XVII is of particular concern due to its uncertain structural condition and due to the level of stress caused by the regional seismicity. Therefore, lifetime assessment, taking into account the evolution of damage phenomena, is necessary to preserve the reliability and safety of this masterpiece of cultural heritage. A continuous AE monitoring was performed to assess the structural behavior of the Chapel. During the monitoring period, a correlation between peaks of AE activity in the masonry of the "Sacred Mountain of Varallo" and regional seismicity was found. Although the two phenomena take place on very different scales, the AE in materials and the earthquakes in Earth's crust, belong to the same class of invariance. In addition, an accurate finite element model, performed with DIANA finite element code, is presented to describe the dynamic behavior of Chapel XVII structure, confirming visual and instrumental inspections of regional seismic effects.

  9. The Sacred Mountain of Varallo in Italy: Seismic Risk Assessment by Acoustic Emission and Structural Numerical Models

    Directory of Open Access Journals (Sweden)

    Alberto Carpinteri

    2013-01-01

    Full Text Available We examine an application of Acoustic Emission (AE technique for a probabilistic analysis in time and space of earthquakes, in order to preserve the valuable Italian Renaissance Architectural Complex named “The Sacred Mountain of Varallo.” Among the forty-five chapels of the Renaissance Complex, the structure of the Chapel XVII is of particular concern due to its uncertain structural condition and due to the level of stress caused by the regional seismicity. Therefore, lifetime assessment, taking into account the evolution of damage phenomena, is necessary to preserve the reliability and safety of this masterpiece of cultural heritage. A continuous AE monitoring was performed to assess the structural behavior of the Chapel. During the monitoring period, a correlation between peaks of AE activity in the masonry of the “Sacred Mountain of Varallo” and regional seismicity was found. Although the two phenomena take place on very different scales, the AE in materials and the earthquakes in Earth’s crust, belong to the same class of invariance. In addition, an accurate finite element model, performed with DIANA finite element code, is presented to describe the dynamic behavior of Chapel XVII structure, confirming visual and instrumental inspections of regional seismic effects.

  10. Investigation of Seismic Behavior of Container Crane Structures by Shake Table Tests and Mathematical Modeling

    Directory of Open Access Journals (Sweden)

    C. Oktay Azeloglu

    2014-01-01

    Full Text Available This paper is concerned with the verification of mathematical modeling of the container cranes under earthquake loadings with shake table test results. Comparison of the shake table tests with the theoretical studies has an important role in the estimation of the seismic behavior of the engineering structures. For this purpose, a new shake table and mathematical model were developed. Firstly, a new physical model is directly fixed on the shake table and the seismic response of the container crane model against the past earthquake ground motion was measured. Secondly, a four degrees-of-freedom mathematical model is developed to understand the dynamic behaviour of cranes under the seismic loadings. The results of the verification study indicate that the developed mathematical model reasonably represents the dynamic behaviour of the crane structure both in time and frequency domains. The mathematical model can be used in active-passive vibration control studies to decrease structural vibrations on container cranes.

  11. The great triangular seismic region in eastern Asia: Thoughts on its dynamic context

    Directory of Open Access Journals (Sweden)

    Xianglin Gao

    2011-01-01

    Full Text Available A huge triangle-shaped tectonic region in eastern Asia plays host to numerous major earthquakes. The three boundaries of this region, which contains plateaus, mountains, and intermountain basins, are roughly the Himalayan arc, the Tianshan-Baikal, and longitude line ∼105°E. Within this triangular region, tectonism is intense and major deformation occurs both between crustal blocks and within most of them. Outside of this region, rigid blocks move as a whole with relatively few major earthquakes and relatively weak Cenozoic deformation. On a large tectonic scale, the presence of this broad region of intraplate deformation results from dynamic interactions between the Indian, Philippine Sea-West Pacific, and Eurasian plates, as well as the influence of deep-level mantle flow. The Indian subcontinent, which continues to move northwards at ∼40 mm/a since its collision with Eurasia, has plunged beneath Tibet, resulting in various movements and deformations along the Himalayan arc that diffuse over a long distance into the hinterland of Asia. The northward crustal escape of Asia from the Himalayan collisional zone turns eastwards and southeastwards along 95°–100°E longitude and defines the eastern Himalayan syntaxis. At the western Himalayan syntaxis, the Pamirs continue to move into central Asia, leading to crustal deformation and earthquakes that are largely accommodated by old EW or NW trending faults in the bordering areas between China, Mongolia, and Russia, and are restricted by the stable landmass northwest of the Tianshan-Altai-Baikal region. The subduction of the Philippine and Pacific plates under the Eurasian continent has generated a very long and narrow seismic zone along trenches and island arcs in the marginal seas while imposing only slight horizontal compression on the Asian continent that does not impede the eastward motion of eastern Asia. In the third dimension, there may be southeastward deep mantle flow beneath most of

  12. Geomechanical modelling of the induced seismicity for a gas field

    NARCIS (Netherlands)

    Orlic, B.; Eijs, R. van; Scheffers, B.

    2001-01-01

    Gas production from a reservoir may lead to reactivation of nearby faults, which is likely to cause local seismic events. This paper is focusing on the calculations of stress evolution during depletion of a gas reservoir in order to investigate the possibilities for the reactivation and slip on norm

  13. Finite Element Modelling of Seismic Liquefaction in Soils

    NARCIS (Netherlands)

    Galavi, V.; Petalas, A.; Brinkgreve, R.B.J.

    2013-01-01

    Numerical aspects of seismic liquefaction in soils as implemented in the finite element code, PLAXIS, is described in this paper. After description of finite element equations of dynamic problems, three practical dynamic boundary conditions, namely viscous boundary tractions, tied degrees of freedom

  14. Finite-difference modeling experiments for seismic interferometry

    NARCIS (Netherlands)

    Thorbecke, J.W.; Draganov, D.

    2011-01-01

    In passive seismic interferometry, new reflection data can be retrieved by crosscorrelating recorded noise data. The quality of the retrieved reflection data is, among others, dependent on the duration and number of passive sources present during the recording time, the source distribution, and the

  15. Seismic waveform inversion best practices: regional, global and exploration test cases

    Science.gov (United States)

    Modrak, Ryan; Tromp, Jeroen

    2016-09-01

    Reaching the global minimum of a waveform misfit function requires careful choices about the nonlinear optimization, preconditioning and regularization methods underlying an inversion. Because waveform inversion problems are susceptible to erratic convergence associated with strong nonlinearity, one or two test cases are not enough to reliably inform such decisions. We identify best practices, instead, using four seismic near-surface problems, one regional problem and two global problems. To make meaningful quantitative comparisons between methods, we carry out hundreds of inversions, varying one aspect of the implementation at a time. Comparing nonlinear optimization algorithms, we find that limited-memory BFGS provides computational savings over nonlinear conjugate gradient methods in a wide range of test cases. Comparing preconditioners, we show that a new diagonal scaling derived from the adjoint of the forward operator provides better performance than two conventional preconditioning schemes. Comparing regularization strategies, we find that projection, convolution, Tikhonov regularization and total variation regularization are effective in different contexts. Besides questions of one strategy or another, reliability and efficiency in waveform inversion depend on close numerical attention and care. Implementation details involving the line search and restart conditions have a strong effect on computational cost, regardless of the chosen nonlinear optimization algorithm.

  16. Statistical analysis and modeling of seismicity related to the exploitation of geothermal energy

    Science.gov (United States)

    Dinske, Carsten; Langenbruch, Cornelius; Shapiro, Serge

    2016-04-01

    Geothermal energy is an integral and important part of renewables but it is frequently observed that its production induces seismicity. Here we analyse in detail seismicity from two hydrothermal reservoirs in Germany and one hydrothermal field in Italy. We focus on temporal changes of seismicity rates. This study was motivated by the results of numerical simulations. The modeling of stress changes caused by the injection and production of fluids revealed that the seismicity rate should decrease on a long-term perspective which does not match the observed seismicity rates. To understand this mismatch we analyse the waiting time distributions of the seismic events in both time domain (inter event times) and fluid volume domain (inter event volume). We find clear indications that the observed seismicity contains two components: (1) seismicity that is directly triggered by the production and re-injection of fluid, in other words, induced events, and (2) seismicity that is triggered by earthquake interactions also known as aftershock triggering. In order to calibrate and better constrain our numerical simulations using the induced seismicity we apply a catalog declustering the separate the two components and remove the aftershocks from the observed catalogs. We use the magnitude-dependent space-time windowing approach introduced by Gardener and Knopoff (1974) and tested several published algorithms to calculate the windows. We choose the final space-time window for a given catalog based on the waiting time distribution of the events after the declustering. Technically speaking, we suppose that the probability density of waiting times in the fluid volume domain corresponds to a homogeneous Poisson process (HPP, Langenbruch et al., 2011). After catalog declustering, we conclude that the different reservoirs show a comparable response to the production and re-injection of fluids and the additional triggering of seismicity by earthquake interactions. The declustered

  17. Features of Seismicity in the Northeastern China Region and Their Relation to the Subduction of the Japan Sea Plate

    Institute of Scientific and Technical Information of China (English)

    Sun Wenbin; He Yueshi

    2004-01-01

    Based on the analyses of grouped activity features of deep-focus (M ≥ 6.0) and shallow-focus(Ms ≥ 5.0) earthquakes in the Northeast China region, the time-space correlation betweendeep focus "strong earthquake group" and shallow focus "strong earthquake group" have beenstudied. The study was mainly on the characteristics of earthquake distribution on the collisionzone between the west Pacific plate and the Eurasian plate and on its relations to themorphological feature of the western Pacific subduction zone. Moreover, emphasis was laid onanalysis of the effect of the west Pacific plate on the seismicity of Eurasian plate. It is shownthat in the region where the west Pacific plate subducts at low angles, the seismicity on theplate collision zone is strong, the effect of plate subduction on Eurasian continent is strong too,and the subduction zone is under a state of high compressional stress. However, in the regionwhere the west Pacific plate subducts at high angles, the seismicity along the plate collision zoneis weak, the effect of plate subduction on Eurasian continent is weak too, and the tensile stressproduced by the subduction zone at depth is enhanced. We therefore propose that the seismicityin the northeast China region will enter an active period of shallow "strong earthquake group"in the future 10 years. In the period, six earthquakes of Ms ≥5.0 may occur. Therefore, the work of earthquake monitoring and prediction in this region shall be strengthened.

  18. Stochastic Earthquake Rupture Modeling Using Nonparametric Co-Regionalization

    Science.gov (United States)

    Lee, Kyungbook; Song, Seok Goo

    2016-10-01

    Accurate predictions of the intensity and variability of ground motions are essential in simulation-based seismic hazard assessment. Advanced simulation-based ground motion prediction methods have been proposed to complement the empirical approach, which suffers from the lack of observed ground motion data, especially in the near-source region for large events. It is important to quantify the variability of the earthquake rupture process for future events and to produce a number of rupture scenario models to capture the variability in simulation-based ground motion predictions. In this study, we improved the previously developed stochastic earthquake rupture modeling method by applying the nonparametric co-regionalization, which was proposed in geostatistics, to the correlation models estimated from dynamically derived earthquake rupture models. The nonparametric approach adopted in this study is computationally efficient and, therefore, enables us to simulate numerous rupture scenarios, including large events (M > 7.0). It also gives us an opportunity to check the shape of true input correlation models in stochastic modeling after being deformed for permissibility. We expect that this type of modeling will improve our ability to simulate a wide range of rupture scenario models and thereby predict ground motions and perform seismic hazard assessment more accurately.

  19. Example of seismic modelling of the Pp and PS modes from well and lithological profile data; Exemplo de modelagem sismica dos modos PP e PS a partir de dados de poco e perfil litologico

    Energy Technology Data Exchange (ETDEWEB)

    Leiderman, R.; Artola, M.B.C. Silva; Silva, M.B.C.; Fontoura, S.A.B. da [Pontificia Universidade Catolica do Rio de Janeiro, RJ (Brazil). Grupo de Tecnologia em Engenharia de Petroleo]. E-mail: artola@civ.puc-rio.br

    2003-07-01

    In order to evaluate the possibility of the using of the PS converted mode for subsoil imaging, and to help to interpret the seismic section generated by the signal processing of the data obtained during a 2D/4C seismic acquisition, a seismic modeling study of the region in which the acquisition took place was realized. A 10 isotropic layers model was built based on well data and on the lithologic profile of the region. The reflectivity of the Pp and PSV modes of each interface of the model was determined. Synthetic seismograms were generated with the aid of the ray-tracing package NORSAR{sup C}. The synthetic seismograms generated show the potentiality of the converted mode to imaging the reflectors as well as allow the identification, in the temporal domain, of the main seismic horizons of the region and correlate them to geologic structures. (author)

  20. 3D models of slow motions in the Earth's crust and upper mantle in the source zones of seismically active regions and their comparison with highly accurate observational data: I. Main relationships

    Science.gov (United States)

    Molodenskii, S. M.; Molodenskii, M. S.; Begitova, T. A.

    2016-09-01

    Constructing detailed models for postseismic and coseismic deformations of the Earth's surface has become particularly important because of the recently established possibility to continuously monitor the tectonic stresses in the source zones based on the data on the time variations in the tidal tilt amplitudes. Below, a new method is suggested for solving the inverse problem about the coseismic and postseismic deformations in the real non-ideally elastic, radially and horizontally heterogeneous, self-gravitating Earth with a hydrostatic distribution of the initial stresses from the satellite data on the ground surface displacements. The solution of this problem is based on decomposing the parameters determining the geometry of the fault surface and the distribution of the dislocation vector on this surface and elastic modules in the source in the orthogonal bases. The suggested approach includes four steps: 1. Calculating (by the perturbation method) the variations in Green's function for the radial and tangential ground surface displacements with small 3D variations in the mechanical parameters and geometry of the source area (i.e., calculating the functional derivatives of the three components of Green's function on the surface from the distributions of the elastic moduli and creep function within the volume of the source area and Burgers' vector on the surface of the dislocations); 2. Successive orthogonalization of the functional derivatives; 3. Passing from the decompositions of the residuals between the observed and modeled surface displacements in the system of nonorthogonalized functional derivatives to their decomposition in the system of orthogonalized derivatives; finding the corrections to the distributions of the sought parameters from the coefficients of their decompositions in the orthogonalized basis; and 4. Analyzing the ambiguity of the inverse problem solution by constructing the orthogonal complement to the obtained basis. The described

  1. Theoretical Study on Stochastic Modeling of Combined Gravity-Magnetic-Electric-Seismic Inversion and Its Application

    Institute of Scientific and Technical Information of China (English)

    Yan Hanjie; Yan Hong; Li Yunping; Zhang Xiaofeng

    2003-01-01

    As gravity field, magnetic field, electric field and reismic wave field are all physical fields, their object function, reverse function and compound function are certainly infinite continuously differentiable functions which can be expanded into Taylor (Fourier) series within domain of definition and be further reduced into solving stochastic distribution function of series and statistic inference of optimal approximation. This is thebasis of combined gravity-magnetic-electric-seismic inversion of stochastic modeling. It is an uncertainty modeling technology of combining gravity-magnetic-electric-seismic inversion built on the basis of separation of field and source gravity-magnetic difference-value (D-value) trend surface, taking distribution-independent fault system as its unit, depths of seismic and electric interfaces of interests as its corresponding bivariate compound reverse function of gravity-magnetic anomalies and using high order polynomial (high order trigonometric function) approximating to its series distribution. The difference from current dominant inversion techniques is that, first, it does not respectively create gravity-seismic, magnetic-seismic deterministic inversion model from theoretical model, but combines gravity-magnetic-electric-seismic stochastic inversion model from stochastic model; second, after the concept of equivalent geological body being introduced, using feature of independent variable of gravity-magnetic field functions, taking density and susceptibility related to gravity-magnetic function as default parameters of model, the deterministic model is established owing to better solution to the contradiction of difficulty in identifying strata and less test analytical data for density and susceptibility in newly explored area; third, under assumption of independent parent distribution, a real modeling by strata, the problem of difficult plane closure arising in profile modeling is avoided. This technology has richer and more

  2. Stochastic representations of seismic anisotropy: transversely isotropic effective media models

    Science.gov (United States)

    Song, Xin; Jordan, Thomas H.

    2017-06-01

    We apply Jordan's self-consistent, second-order Born theory to compute the effective stiffness tensor for spatially stationary, stochastic models of 3-D elastic heterogeneity. The effects of local anisotropy can be separated from spatially extended geometric anisotropy by factoring the covariance of the moduli into a one-point variance tensor and a two-point correlation function. The latter is incorporated into the rescaled Kneer tensor, which is contracted against the one-point variance tensor to yield a second-order perturbation to the Voigt average. The theory can handle heterogeneity with orthotropic stochastic symmetry, but the calculations presented here are restricted to media with transversely isotropic (TI) statistics. We thoroughly investigate TI stochastic media that are locally isotropic. If the heterogeneity aspect ratio η is unity, the effective medium is isotropic, and the main effect of the scattering is to reduce the moduli. The two limiting regimes are a 2-D vertical stochastic bundle (η → 0), where the P and S anisotropy ratios are negative, and a 1-D horizontal stochastic laminate (η → ∞), where they are positive. The effective-medium equations for the latter yield the second-order approximation to Backus's exact solution, demonstrating the connection between Backus theory and self-consistent effective-media theory. Comparisons of the exact and second-order results for non-Gaussian laminates indicate that the approximation should be adequate for moduli heterogeneities less than about 30 per cent and thus valid for most seismological purposes. We apply the locally isotropic theory to data from the Los Angeles Basin to illustrate how it can be used to explain shallow seismic anisotropy. To assess the relative contributions of geometric and local anisotropy to the effective anisotropy, we consider a rotational model for stochastic anisotropic variability proposed by Jordan. In this model, the axis of a hexagonally symmetric stiffness

  3. Body wave travel times and amplitudes for present-day seismic model of Mars

    Science.gov (United States)

    Raevskiy, Sergey; Gudkova, Tamara

    At the moment Martian interior structure models are constrained by the satellite observational data (the mass, the moment of inertia factor, the Love number k _{2}) (Konopliv et al., 2011) and high pressure experimental data (Bertka and Fei, 1997). Seismological observations could provide unparalleled capability for studying Martian interiors. Future missions include seismic experiments on Mars (Lognonné et al., 2012). The main instrument for these seismic experiments is a broadband seismometer (Robert et al., 2012). When seismic measurements are not yet available, physically consistent interior models, characterized by properties of relevant minerals, make possible to study of the seismic response of the planet. \\To estimate travel times for direct P, S, core reflected PcP, ScS and core refracted PKP body waves as a function of epicentral distance and hypocentral depth, as well as their amplitudes at the surface for a given marsquake, software product was developed in MatLab, as it encompasses many plotting routines that plot resulting travel times and ray paths. The computational results have been compared with the program TTBox (Knapmeyer, 2004). The code computes seismic ray paths and travel times for a one-dimentional spherical interior model (density and seismic velocities are functions of a radius only). Calculations of travel times tables for direct P, S, core reflected PcP, ScS and core refracted PKP waves and their amplitudes are carried out for a trial seismic model of Mars M14_3 from (Zharkov et al., 2009): the core radius is 1800 km, the thickness of the crust is 50 km. Direct and core reflected P and S waves are recorded to a maximum epicentral distance equal to about 100(°) , and PKP arrivals can be detected for epicental distances larger than 150(°) . The shadow zone is getting wider in comparison with previous results (Knapmeyer, 2010), as the liquid core radius of the seismic model under consideration is larger. Based on the estimates of

  4. Recording and investigation of the seismic signal generated by hypervelocity impact experiments and numerical models

    Science.gov (United States)

    Güldemeister, N.; Moser, D.; Wünnemann, K.; Hoerth, T.; Schäfer, F.

    2013-09-01

    Meteorite impacts can cause environmental consequences, one of which is the generation of ground motions that may exceed the magnitude of the largest earthquakes [1]. Impacts generate shock waves that attenuate with distance until they even tually turn into seismic waves. Thus, meteorite impact may be considered as a source for seismic shaking similar to earthquakes. Seismic signals have been recorded in explosion experiments [2] and in hydrocode models of large impact events such as the Chicxulub crater [3]. To determine how much of the kinetic energy Ekin of the impactoris turned into seismic energy Eseis can be investigated experimentally (by recording the acoustic emission) or by numerical models. The ratio of Eseis/Ekin is the so called seismic efficiency k. The seismic efficiency depends on material properties (porosity) and is usually estimated to range between 10-2 and 10-6 [2,4]. In the framework of the "MEMIN" (multidisciplinary experimental and modeling impact crater research network) project a suite of hypervelocity impact experiments on a decimeter scale have been carried out [5]. We use acoustic emission (AE) technique and pressure gauges in high spatiotemporal Meteorite impacts can cause environmental consequences, one of which is the generation of ground motions that may exceed the magnitude of the largest earthquakes [1]. Impacts generate shock waves that attenuate with distance until they even tually turn into seismic waves. Thus, meteorite impact may be considered as a source for seismic shaking similar to earthquakes. Seismic signals have been recorded in explosion experiments [2] and in hydrocode models of large impact events such as the Chicxulub crater [3]. To determine how much of the kinetic energy Ekin of the impactoris turned into seismic energy Eseis can be investigated experimentally (by recording the acoustic emission) or by numerical models. The ratio of Eseis/Ekin is the so called seismic efficiency k. The seismic efficiency depends

  5. A GIS-based time-dependent seismic source modeling of Northern Iran

    Science.gov (United States)

    Hashemi, Mahdi; Alesheikh, Ali Asghar; Zolfaghari, Mohammad Reza

    2017-01-01

    The first step in any seismic hazard study is the definition of seismogenic sources and the estimation of magnitude-frequency relationships for each source. There is as yet no standard methodology for source modeling and many researchers have worked on this topic. This study is an effort to define linear and area seismic sources for Northern Iran. The linear or fault sources are developed based on tectonic features and characteristic earthquakes while the area sources are developed based on spatial distribution of small to moderate earthquakes. Time-dependent recurrence relationships are developed for fault sources using renewal approach while time-independent frequency-magnitude relationships are proposed for area sources based on Poisson process. GIS functionalities are used in this study to introduce and incorporate spatial-temporal and geostatistical indices in delineating area seismic sources. The proposed methodology is used to model seismic sources for an area of about 500 by 400 square kilometers around Tehran. Previous researches and reports are studied to compile an earthquake/fault catalog that is as complete as possible. All events are transformed to uniform magnitude scale; duplicate events and dependent shocks are removed. Completeness and time distribution of the compiled catalog is taken into account. The proposed area and linear seismic sources in conjunction with defined recurrence relationships can be used to develop time-dependent probabilistic seismic hazard analysis of Northern Iran.

  6. Distribution Characteristics of the Seismicity of Zipingpu Reservoir Region after the Wenchuan Earthquake

    Institute of Scientific and Technical Information of China (English)

    Li Hai'ou; Ma Wentao; Xu Xiwei; Xie Ronghua; Yuan Jingli; Xu Changpeng

    2011-01-01

    815 earthquakes recorded by 12 seismic stations of the Zipingpu reservoir seismic network in 2009 were relocated using the double difference algorithm to analyze the seismic activity of the Zipingpu reservoir. Relocation results show that the earthquakes are concentrated relatively in three zones. The distribution characteristics of focal depth are obviously different among different concentration zones. This means earthquakes in different concentration zones may have different causes. Compared to relocation of earthquakes taking place before the Wenchuan earthquake done by other researchers, the seismic concentration zones in the reservoir area shifted obviously after the Wenchuan earthquake. These variations are related to local stress adjustment in the reservoir area and may also be related to the diffusion depth and range of increased pore pressure caused by rock failure in the course of Wenchuan earthquake.

  7. Structure of the Koyna-Warna Seismic Zone, Maharashtra, India: A possible model for large induced earthquakes elsewhere

    Science.gov (United States)

    Catchings, Rufus D.; Dixit, M.M.; Goldman, Mark R.; Kumar, S.

    2015-01-01

    The Koyna-Warna area of India is one of the best worldwide examples of reservoir-induced seismicity, with the distinction of having generated the largest known induced earthquake (M6.3 on 10 December 1967) and persistent moderate-magnitude (>M5) events for nearly 50 years. Yet, the fault structure and tectonic setting that has accommodated the induced seismicity is poorly known, in part because the seismic events occur beneath a thick sequence of basalt layers. On the basis of the alignment of earthquake epicenters over an ~50 year period, lateral variations in focal mechanisms, upper-crustal tomographic velocity images, geophysical data (aeromagnetic, gravity, and magnetotelluric), geomorphic data, and correlation with similar structures elsewhere, we suggest that the Koyna-Warna area lies within a right step between northwest trending, right-lateral faults. The sub-basalt basement may form a local structural depression (pull-apart basin) caused by extension within the step-over zone between the right-lateral faults. Our postulated model accounts for the observed pattern of normal faulting in a region that is dominated by north-south directed compression. The right-lateral faults extend well beyond the immediate Koyna-Warna area, possibly suggesting a more extensive zone of seismic hazards for the central India area. Induced seismic events have been observed many places worldwide, but relatively large-magnitude induced events are less common because critically stressed, preexisting structures are a necessary component. We suggest that releasing bends and fault step-overs like those we postulate for the Koyna-Warna area may serve as an ideal tectonic environment for generating moderate- to large- magnitude induced (reservoir, injection, etc.) earthquakes.

  8. Developments of Finite-Frequency Seismic Theory and Applications to Regional Tomographic Imaging

    Science.gov (United States)

    2009-01-31

    Seism . Soc. Am. 94, 1690–1705, doi 10.1785/012004016. Kennett, B. L. N. (1983). Seismic Wave Propagation in Stratified Media, Cambridge University...Vilotte (1998). The spectral-element method: an efficient tool to simulate the seismic response of 2D and 3D, geolog- ical structures, Bull. Seism ...Crosson (1990). Determination of teleseismic relative phase arrival times using multi-channel cross-correlation and least squares, Bull. Seism . Soc

  9. New Frontiers on Seismic Modeling of Masonry Structures

    Directory of Open Access Journals (Sweden)

    Salvatore Caddemi

    2017-07-01

    Full Text Available An accurate evaluation of the non-linear behavior of masonry structural elements in existing buildings still represents a complex issue that rigorously requires non-linear finite element strategies difficult to apply to real large structures. Nevertheless, for the static and seismic assessment of existing structures, involving the contribution of masonry materials, engineers need reliable and efficient numerical tools, whose complexity and computational demand should be suitable for practical purposes. For these reasons, the formulation and the validation of simplified numerical strategies represent a very important issue in masonry computational research. In this paper, an innovative macroelement approach, developed by the authors in the last decade, is presented. The proposed macroelement formulation is based on different, plane and spatial, macroelements for the simulation of both the in-plane and out-of-plane behavior of masonry structures also in presence of masonry elements with curved geometry. The mechanical response of the adopted macroelement is governed by non-linear zero-thickness interfaces, whose calibration follows a straightforward fiber discretization, and the non-linear internal shear deformability is ruled by equivalence with a corresponding geometrically consistent homogenized medium. The approach can be considered as “parsimonious” since the kinematics of the adopted elements is controlled by very few degrees of freedom, if compared to a corresponding discretization performed by using non-linear finite element method strategies. This innovative discrete element strategy has been implemented in two user-oriented software codes 3DMacro (Caliò et al., 2012b and HiStrA (Historical Structures Analysis (Caliò et al., 2015, which simplify the modeling of buildings and historical structures by means of several wizard generation tools and input/output facilities. The proposed approach, that represents a powerful tool for the

  10. Spatio-Temporal Modeling of Seismic Provinces of Iran Using DBSCAN Algorithm

    Science.gov (United States)

    Kazemi-Beydokhti, Mohammad; Ali Abbaspour, Rahim; Mojarab, Masoud

    2017-05-01

    One of the most important issues in the field of engineering seismology is identification and classification of seismic provinces. Due to the importance of this issue in Iran, various studies have been conducted using different methods such as expert judgment, computational methods, data-driven methods, and smart methods. The purpose of the present research is to develop a spatio-temporal seismic model for Iran using robust and objective clustering tools. In the present study, one of the most powerful clustering methods, DBSCAN, is selected based on its ability to analyze huge amounts of data. The DBSCAN algorithm, which acts based on the density of seismic events, is capable of detecting arbitrarily shaped clusters. The seismic datasets used in this study, which were obtained from the seismic catalog of Iran from 1900 to 2015, have been divided into three window periods including 2- , 5- , and 10-year intervals. Afterward, different seismicity patterns for each period are obtained by applying DBSCAN algorithm. Then, those exhibited high agreements in terms of shapes and locations of clusters with the other models are determined. Ultimately, by considering these models and using expert judgments, a unified spatio-temporal model is presented. The results reveal meaningful information in different parts of Iran especially in Zagros, Alborz, and Azerbaijan zones and are generally in good agreement with previous studies. Moreover, the results emphasize that a seismic model, which is obtained based on considering seismogenic zones in various time periods along with the application of density-based clustering tools, will produce reliable results.

  11. Spatio-Temporal Modeling of Seismic Provinces of Iran Using DBSCAN Algorithm

    Science.gov (United States)

    Kazemi-Beydokhti, Mohammad; Ali Abbaspour, Rahim; Mojarab, Masoud

    2017-03-01

    One of the most important issues in the field of engineering seismology is identification and classification of seismic provinces. Due to the importance of this issue in Iran, various studies have been conducted using different methods such as expert judgment, computational methods, data-driven methods, and smart methods. The purpose of the present research is to develop a spatio-temporal seismic model for Iran using robust and objective clustering tools. In the present study, one of the most powerful clustering methods, DBSCAN, is selected based on its ability to analyze huge amounts of data. The DBSCAN algorithm, which acts based on the density of seismic events, is capable of detecting arbitrarily shaped clusters. The seismic datasets used in this study, which were obtained from the seismic catalog of Iran from 1900 to 2015, have been divided into three window periods including 2- , 5- , and 10-year intervals. Afterward, different seismicity patterns for each period are obtained by applying DBSCAN algorithm. Then, those exhibited high agreements in terms of shapes and locations of clusters with the other models are determined. Ultimately, by considering these models and using expert judgments, a unified spatio-temporal model is presented. The results reveal meaningful information in different parts of Iran especially in Zagros, Alborz, and Azerbaijan zones and are generally in good agreement with previous studies. Moreover, the results emphasize that a seismic model, which is obtained based on considering seismogenic zones in various time periods along with the application of density-based clustering tools, will produce reliable results.

  12. Building robust models to forecast the induced seismicity related to geothermal reservoir enhancement

    Science.gov (United States)

    Mena Cabrera, B.; Wiemer, S.; Bachmann, C. E.

    2012-04-01

    We test the Epistemic Type Aftershock Sequence, (ETAS) and the Reasenberg and Jones (R&J) models, which are the commonly used models for aftershock forecasting, for the induced seismicity sequence of the Enhanced Geothermal System (EGS) in Basel, in a pseudo-prospective manner. In addition to these two statistical models, we introduce the model of Shapiro et al. (2010) for forecasting induced seismicity due to EGS in a pseudo-prospective modeling approach. While the ETAS and the R&J models are statistical models, the model of Shapiro et al. (2010) is physics based method that takes into account the flow-rate and the seismogenic index that characterizes the level of seismic activity expected from injecting fluid into rock. We aim to define a weighted logic tree approach as input for induced seismicity probabilistic seismic hazard assessment. High performance forecast models defined in a weighted logic tree approach and then converted into time dependent probabilistic seismic hazard can feed probabilistic alarm systems for EGS experiments. We forecast the seismicity rates of the next six hours based on these three model classes using different modeling and updating strategies. We quantitatively test the performances of the models and define a combined model constructed using Akaike weights. We show that such performance testing can be used as an indication for logic tree weighting. We also evaluate the performances of different models in forecasting a certain magnitude/magnitude range (for instance number of events with M≥2 that are of more concern). In addition, we perform a test on how well we can forecast during and post injection seismicity, with the very first coming data (first day or days). This initial testing with recordings of limited time can reveal the suitability of a site for full reservoir stimulation. Robust forecast models can lead us to an early operation of the traffic light system where a decision on continuing/slowing-down/stopping of fluid

  13. Shortcomings of the Winkler Model in the Assessment of Sectioned Tunnels under Seismic Loading

    DEFF Research Database (Denmark)

    Andersen, Lars; Lyngs, J. H.

    2009-01-01

    A Winkler-type model is often applied in the design of tunnels subject to seismic loading. Since the subgrade stiffness is modelled by disjoint springs, distributed continuously along the tunnel, the model does not account for retroaction via the soil. This may not be a problem in the design...

  14. Shortcomings of the Winkler Model in the Assessment of Sectioned Tunnels under Seismic Loading

    DEFF Research Database (Denmark)

    Andersen, Lars; Lyngs, Jakob Hausgaard

    A Winkler-type model is often applied in the design of tunnels subject to seismic loading. Since the subgrade stiffness is modelled by disjoint springs, distributed continuously along the tunnel, the model does not account for retroaction via the soil. This may not be a problem in the design...

  15. Exploring the Gross Schoenebeck (Germany) geothermal site using a statistical joint interpretation of magnetotelluric and seismic tomography models

    Energy Technology Data Exchange (ETDEWEB)

    Munoz, Gerard; Bauer, Klaus; Moeck, Inga; Schulze, Albrecht; Ritter, Oliver [Deutsches GeoForschungsZentrum (GFZ), Telegrafenberg, 14473 Potsdam (Germany)

    2010-03-15

    Exploration for geothermal resources is often challenging because there are no geophysical techniques that provide direct images of the parameters of interest, such as porosity, permeability and fluid content. Magnetotelluric (MT) and seismic tomography methods yield information about subsurface distribution of resistivity and seismic velocity on similar scales and resolution. The lack of a fundamental law linking the two parameters, however, has limited joint interpretation to a qualitative analysis. By using a statistical approach in which the resistivity and velocity models are investigated in the joint parameter space, we are able to identify regions of high correlation and map these classes (or structures) back onto the spatial domain. This technique, applied to a seismic tomography-MT profile in the area of the Gross Schoenebeck geothermal site, allows us to identify a number of classes in accordance with the local geology. In particular, a high-velocity, low-resistivity class is interpreted as related to areas with thinner layers of evaporites; regions where these sedimentary layers are highly fractured may be of higher permeability. (author)

  16. Compilation of a recent seismicity data base of the greater Alpine region from several seismological networks and preliminary 3D tomographic results

    Directory of Open Access Journals (Sweden)

    M. Granet

    1997-06-01

    Full Text Available Local earthquake data collected by seven national and regional seismic networks have been compiled into a travel time catalog of 32341 earthquakes for the period 1980 to 1995 in South-Central Europe. As a prerequisite, a complete and corrected station list (master station list has been prepared according to updated information provided by every network. By simultaneous inversion of some 600 well-locatable events we obtained one-dimensional (1D velocity propagation models for each network. Consequently, these velocity models with appropriate station corrections have been used to obtain high-quality hypocenter locations for events inside and among the station networks. For better control, merging of phase data from several networks was performed as an iterative process where at each iteration two data sets of neighbouring networks or groups of networks were merged. Particular care was taken to detect and correctly identify phase data from events common to data sets from two different networks. In case of reports of the same phase data from more than one network, the phase data from the network owning and servicing the station were used according to the master station list. The merging yielded a data set of 278007 P and 191074 S-wave travel time observations from 32341 events in the greater Alpine region. Restrictive selection (number of P-wave observations >7; gap <160 degrees yielded a data set of about 10000 events with a total of more than 128000 P and 87000 S-wave observations well suited for local earthquake seismic tomography study. Preliminary tomographic results for South-Central Europe clearly show the topography of the crust-mantle boundary in the greater Alpine region and outline the 3D structure of the seismic Ivrea body.

  17. A physics-based earthquake simulator and its application to seismic hazard assessment in Calabria (Southern Italy) region

    Science.gov (United States)

    Console, Rodolfo; Nardi, Anna; Carluccio, Roberto; Murru, Maura; Falcone, Giuseppe; Parsons, Thomas E.

    2017-01-01

    The use of a newly developed earthquake simulator has allowed the production of catalogs lasting 100 kyr and containing more than 100,000 events of magnitudes ≥4.5. The model of the fault system upon which we applied the simulator code was obtained from the DISS 3.2.0 database, selecting all the faults that are recognized on the Calabria region, for a total of 22 fault segments. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which can be compared with those of the real observations. The results of the physics-based simulator algorithm were compared with those obtained by an alternative method using a slip-rate balanced technique. Finally, as an example of a possible use of synthetic catalogs, an attenuation law has been applied to all the events reported in the synthetic catalog for the production of maps showing the exceedance probability of given values of PGA on the territory under investigation.

  18. A physics-based earthquake simulator and its application to seismic hazard assessment in Calabria (Southern Italy) region

    Science.gov (United States)

    Console, Rodolfo; Nardi, Anna; Carluccio, Roberto; Murru, Maura; Falcone, Giuseppe; Parsons, Thomas E.

    2017-01-01

    The use of a newly developed earthquake simulator has allowed the production of catalogs lasting 100 kyr and containing more than 100,000 events of magnitudes ≥4.5. The model of the fault system upon which we applied the simulator code was obtained from the DISS 3.2.0 database, selecting all the faults that are recognized on the Calabria region, for a total of 22 fault segments. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which can be compared with those of the real observations. The results of the physics-based simulator algorithm were compared with those obtained by an alternative method using a slip-rate balanced technique. Finally, as an example of a possible use of synthetic catalogs, an attenuation law has been applied to all the events reported in the synthetic catalog for the production of maps showing the exceedance probability of given values of PGA on the territory under investigation.

  19. Long-term seismicity of the Reykjanes Ridge (North Atlantic) recorded by a regional hydrophone array

    Science.gov (United States)

    Goslin, Jean; Lourenço, Nuno; Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Haxel, Joe; Luis, Joaquim

    2005-08-01

    The seismicity of the northern Mid-Atlantic Ridge was recorded by two hydrophone networks moored in the sound fixing and ranging (SOFAR) channel, on the flanks of the Mid-Atlantic Ridge, north and south of the Azores. During its period of operation (05/2002-09/2003), the northern `SIRENA' network, deployed between latitudes 40° 20'N and 50° 30'N, recorded acoustic signals generated by 809 earthquakes on the hotspot-influenced Reykjanes Ridge. This activity was distributed between five spatio-temporal event clusters, each initiated by a moderate-to-large magnitude (4.0-5.6 M) earthquake. The rate of earthquake occurrence within the initial portion of the largest sequence (which began on 2002 October 6) is described adequately by a modified Omori law aftershock model. Although this is consistent with triggering by tectonic processes, none of the Reykjanes Ridge sequences are dominated by a single large-magnitude earthquake, and they appear to be of relatively short duration (0.35-4.5 d) when compared to previously described mid-ocean ridge aftershock sequences. The occurrence of several near-equal magnitude events distributed throughout each sequence is inconsistent with the simple relaxation of mainshock-induced stresses and may reflect the involvement of magmatic or fluid processes along this deep (>2000 m) section of the Reykjanes Ridge.

  20. Seismic quiescence and b-value decrease before large events in forest-fire model

    CERN Document Server

    Mitsudo, Tetsuya; Kato, Naoyuki

    2015-01-01

    Forest fire models may be interpreted as a simple model for earthquake occurrence by translating trees and fire into stressed segments of a fault and their rupture, respectively. Here we adopt a twodimensional forest-fire model in continuous time, and focus on the temporal changes of seismicity and the b-value. We find the b-value change and seismic quiescence prior to large earthquakes by stacking many sequences towards large earthquakes. As the magnitude-frequency relation in this model is directly related to the cluster-size distribution, decrease of the b-value can be explained in terms of the change in the cluster-size distribution. Decrease of the b-value means that small clusters of stressed sites aggregate into a larger cluster. Seismic quiescence may be attributed to the decrease of stressed sites that do not belong to percolated clusters.

  1. Time-lapse seismic waveform modelling and attribute analysis using hydromechanical models for a deep reservoir undergoing depletion

    Science.gov (United States)

    He, Y.-X.; Angus, D. A.; Blanchard, T. D.; Wang, G.-L.; Yuan, S.-Y.; Garcia, A.

    2016-04-01

    Extraction of fluids from subsurface reservoirs induces changes in pore pressure, leading not only to geomechanical changes, but also perturbations in seismic velocities and hence observable seismic attributes. Time-lapse seismic analysis can be used to estimate changes in subsurface hydromechanical properties and thus act as a monitoring tool for geological reservoirs. The ability to observe and quantify changes in fluid, stress and strain using seismic techniques has important implications for monitoring risk not only for petroleum applications but also for geological storage of CO2 and nuclear waste scenarios. In this paper, we integrate hydromechanical simulation results with rock physics models and full-waveform seismic modelling to assess time-lapse seismic attribute resolution for dynamic reservoir characterization and hydromechanical model calibration. The time-lapse seismic simulations use a dynamic elastic reservoir model based on a North Sea deep reservoir undergoing large pressure changes. The time-lapse seismic traveltime shifts and time strains calculated from the modelled and processed synthetic data sets (i.e. pre-stack and post-stack data) are in a reasonable agreement with the true earth models, indicating the feasibility of using 1-D strain rock physics transform and time-lapse seismic processing methodology. Estimated vertical traveltime shifts for the overburden and the majority of the reservoir are within ±1 ms of the true earth model values, indicating that the time-lapse technique is sufficiently accurate for predicting overburden velocity changes and hence geomechanical effects. Characterization of deeper structure below the overburden becomes less accurate, where more advanced time-lapse seismic processing and migration is needed to handle the complex geometry and strong lateral induced velocity changes. Nevertheless, both migrated full-offset pre-stack and near-offset post-stack data image the general features of both the overburden and

  2. Self-consistent seismic cycle simulation in a three-dimensional continuum model: methodology and examples.

    Science.gov (United States)

    Pranger, C. C.; Le Pourhiet, L.; May, D.; van Dinther, Y.; Gerya, T.

    2016-12-01

    Subduction zones evolve over millions of years. The state of stress, the distribution of materials, and the strength and structure of the interface between the two plates is intricately tied to a host of time-dependent physical processes, such as damage, friction, (nonlinear) viscous relaxation, and fluid migration. In addition, the subduction interface has a complex three-dimensional geometry that evolves with time and can adjust in response to a changing stress environment or in response to impinging topographical features, and can even branch off as a splay fault. All in all, the behaviour of (large) earthquakes at the millisecond to minute timescale is heavily dependent on the pattern of stress accumulation during the 100 year inter-seismic period, the events occurring on or near the interface in the past thousands of years, as well as the extended geological history of the region. We address the aforementioned modeling requirements by developing a self-consistent 3D staggered grid finite difference continuum description of motion, thermal advection-diffusion, and poro-visco-elastic two-phase flow. Faults are modelled as plastic shear bands that can develop and evolve in response to a changing stress environment without having a prescribed geometry. They obey a Mohr-Coulomb or Drucker-Prager yield criterion and a rate-and-state friction law. For a sound treatment of plasticity, we borrow elements from mechanical engineering, and extend these with high-quality nonlinear iteration schemes and adaptive time-stepping to resolve the rupture process at all time scales. We will present these techniques together with proof-of-concept examples of self-consistently developing seismic cycles in 2D and 3D, including phases of stress accumulation, fault nucleation, dynamic rupture, and healing.

  3. Application of Seismic Data to Reservoir Modeling of the Chegu 201 Block

    Institute of Scientific and Technical Information of China (English)

    CaiYi; ZhangXiangzhong; ZhangXinshang

    2005-01-01

    Great uncertainty exists in reservoir models built for blocks where well spacing is uneven or large. The uncertainty in reservoir models can be significantly reduced by using Coordinate Cokriging Sequential Gaussian Simulation technology, in combination with the restriction of seismic characteristic data. Satisfactory reservoir parameter interpolation results, which are more accurate than those derived only from borehole data, are obtained, giving rise to a reasonable combination of widespread and dense-sampled seismic (soft data) data with borehole data (hard data). A significant effect has been made in reservoir parameter modeling in the Chegu 201 block of the Futai Oilfield by using this technology.

  4. Geological and Geophysical Models Underneath Bucharest City Responsible for the Variability of Seismic Site Effects

    Science.gov (United States)

    Bala, A.; Aldea, A.; Balan, S. F.; Arion, C.

    2012-04-01

    Bucharest, the capital of Romania, with more than 2 million inhabitants, is considered after Istanbul the second-most earthquake-endangered metropolis in Europe. It is identified as a natural disaster hotspot by a recent global study of the World Bank and the Columbia University (Dilley et al., 2005). Four major earthquakes with moment-magnitudes between 6.9 and 7.7 hit Bucharest in the last 65 years. The most recent destructive earthquake of 4. March 1977, with a moment magnitude of 7.4, caused about 1.500 casualties in the capital alone. All disastrous earthquakes are generated within a small epicentral area - the Vrancea region - about 150 km north-east of Bucharest. Thick unconsolidated sedimentary layers in the area of Bucharest amplify the arriving seismic shear-waves causing severe destruction. Most of the PGA variation across the city is due to the package of the Quaternary sedimentary layers which amplify the original strong motion arrived from the earthquake. The largest amplification of the soil will occur at the lowest natural frequency or its fundamental period. In situ measurements of shear wave velocity in the soil and the soil thickness, provide a rough measurement of the characteristic site period. Extensively seismic noise measurements proved to be a much accessible method and computed H/V spectral ratio over large periods of time, may provide a good indication on the fundamental period of the site, even if the position of the bedrock is not well defined. Within the NATO-funded Science for Peace Project 981882 "Site-effect analyses for the earthquake-endangered metropolis Bucharest, Romania" the drilling and the Vp and Vs (seismic longitudinal and shear-wave velocities) measurements in ten boreholes were done in the years 2006-2008 (Bala et al., 2010). Rock samples were taken from each borehole at different depths for laboratory tests to determine the geotechnical parameters of each sedimentary rock type at the sites. Thus a valuable data base is

  5. CyberShake: A Physics-Based Seismic Hazard Model for Southern California

    Science.gov (United States)

    Graves, R.; Jordan, T.H.; Callaghan, S.; Deelman, E.; Field, E.; Juve, G.; Kesselman, C.; Maechling, P.; Mehta, G.; Milner, K.; Okaya, D.; Small, P.; Vahi, K.

    2011-01-01

    CyberShake, as part of the Southern California Earthquake Center's (SCEC) Community Modeling Environment, is developing a methodology that explicitly incorporates deterministic source and wave propagation effects within seismic hazard calculations through the use of physics-based 3D ground motion simulations. To calculate a waveform-based seismic hazard estimate for a site of interest, we begin with Uniform California Earthquake Rupture Forecast, Version 2.0 (UCERF2.0) and identify all ruptures within 200 km of the site of interest. We convert the UCERF2.0 rupture definition into multiple rupture variations with differing hypocenter locations and slip distributions, resulting in about 415,000 rupture variations per site. Strain Green Tensors are calculated for the site of interest using the SCEC Community Velocity Model, Version 4 (CVM4), and then, using reciprocity, we calculate synthetic seismograms for each rupture variation. Peak intensity measures are then extracted from these synthetics and combined with the original rupture probabilities to produce probabilistic seismic hazard curves for the site. Being explicitly site-based, CyberShake directly samples the ground motion variability at that site over many earthquake cycles (i. e., rupture scenarios) and alleviates the need for the ergodic assumption that is implicitly included in traditional empirically based calculations. Thus far, we have simulated ruptures at over 200 sites in the Los Angeles region for ground shaking periods of 2 s and longer, providing the basis for the first generation CyberShake hazard maps. Our results indicate that the combination of rupture directivity and basin response effects can lead to an increase in the hazard level for some sites, relative to that given by a conventional Ground Motion Prediction Equation (GMPE). Additionally, and perhaps more importantly, we find that the physics-based hazard results are much more sensitive to the assumed magnitude-area relations and

  6. Study on the relationship between geothermal exploitation and seismic activity in Xi'an region

    Institute of Scientific and Technical Information of China (English)

    吴富春; 宋立胜; 朱兴国; 王锋; 景北科; 董星宏; 方炜; 左永青

    2001-01-01

    Based on the analysis of the induced earthquakes in China and abroad, we get some ideas about earthquakes induced by pumping water out of a well or injecting water into a well. The induced earthquakes usually occur near the well, and they are generally small earthquakes. The earthquake sources are shallow, and they belong to the main shock-after shock type of earthquake or the swarm-type of earthquake. The magnitude and the quantity of the induced earthquakes obviously depend on the pressure and the quantity of water pumped or injected. These earthquakes happen as soon as pumping or injecting occurrence, or after ten or twenty days, they may occur at the time of injecting mud or injecting high pressure water when a well is being drilled, or at the time when the ground water is being normally exploited. A large quantity of hot water has been exploited since 1990 in Xi'an, and the quantity of water exploited has been increasing year by year, as a result the groundwater level has been dropping with the water pumped out and the water level is high in summer and low in winter. The earthquakes in Xi'an region belong to the solitary-type and they spread outside Xi'an city where the wells are concentrated but no earthquake happens.The seismic frequency and the energy released have no relation with the quantity of water exploitation or the water level in the well. It is considered that geothermal exploitation does not induce earthquakes in and around Xi'an because of its specially geological condition.

  7. Delineation of seismic source zones based on seismicity parameters and probabilistic evaluation of seismic hazard using logic tree approach

    Indian Academy of Sciences (India)

    K S Vipin; T G Sitharam

    2013-06-01

    The delineation of seismic source zones plays an important role in the evaluation of seismic hazard. In most of the studies the seismic source delineation is done based on geological features. In the present study, an attempt has been made to delineate seismic source zones in the study area (south India) based on the seismicity parameters. Seismicity parameters and the maximum probable earthquake for these source zones were evaluated and were used in the hazard evaluation. The probabilistic evaluation of seismic hazard for south India was carried out using a logic tree approach. Two different types of seismic sources, linear and areal, were considered in the present study to model the seismic sources in the region more precisely. In order to properly account for the attenuation characteristics of the region, three different attenuation relations were used with different weightage factors. Seismic hazard evaluation was done for the probability of exceedance (PE) of 10% and 2% in 50 years. The spatial variation of rock level peak horizontal acceleration (PHA) and spectral acceleration (Sa) values corresponding to return periods of 475 and 2500 years for the entire study area are presented in this work. The peak ground acceleration (PGA) values at ground surface level were estimated based on different NEHRP site classes by considering local site effects.

  8. Observed inflation-deflation cycles at Popocatepetl volcano using tiltmeters and its possible correlation with regional seismic activity in Mexico

    Science.gov (United States)

    Contreras Ruiz Esparza, M. G., Sr.; Jimenez Velazquez, J. C., Sr.; Valdes Gonzalez, C. M., Sr.; Reyes Pimentel, T. A.; Galaviz Alonso, S. A.

    2014-12-01

    Popocatepetl, the smoking mountain, is a stratovolcano located in central Mexico with an elevation of 5450 masl. The active volcano, close to some of the largest urban centers in Mexico - 60 km and 30 km far from Mexico City and Puebla, respectively - poses a high hazard to an estimated population of 500 thousand people living in the vicinity of the edifice. Accordingly, in July 1994 the Popocatepetl Volcanological Observatory (POVO) was established. The observatory is operated and supported by the National Center for Disaster Prevention of Mexico (CENAPRED), and is equipped to fully monitor different aspects of the volcanic activity. Among the instruments deployed, we use in this investigation two tiltmometers and broad-band seismometers at two sites (Chipiquixtle and Encinos), which send the information gathered continuously to Mexico City.In this research, we study the characteristics of the tiltmeters signals minutes after the occurrence of certain earthquakes. The Popocatepetl volcano starts inflation-deflation cycles due to the ground motion generated by events located at certain regions. We present the analysis of the tiltmeters and seismic signals of all the earthquakes (Mw>5) occurred from January 2013 to June 2014, recorded at Chipiquixtle and Encinos stations. First, we measured the maximum tilt variation after each earthquake. Next, we apply a band-pass filter for different frequency ranges to the seismic signals of the two seismic stations, and estimated the total energy of the strong motion phase of the seismic record. Finally, we compared both measurements and observed that the maximum tilt variations were occurring when the maximum total energy of the seismic signals were in a specific frequency range. We also observed that the earthquake records that have the maximum total energy in that frequency range were the ones with a epicentral location south-east of the volcano. We conclude that our observations can be used set the ground for an early

  9. Source processes at the Chilean subduction region: a comparative analysis of recent large earthquakes seismic sequences in Chile

    Science.gov (United States)

    Cesca, Simone; Tolga Sen, Ali; Dahm, Torsten

    2016-04-01

    Large intraplate megathrust events are common at the western margin of the Southamerican plate, and repeatedly affected the slab segment along Chile, driven by the subduction of the oceanic Nazca plate, with a convergence of almost 7 cm/y. The size and rate of seismicity, including the 1960 Mw 9.5 Chile earthquake, pose Chile among the most highly seismogenic regions worldwide. At the same time, thanks to the significant national and international effort in recent years, Chile is nowadays seismologically well equipped and monitored; the dense seismological network provides a valuable dataset to analyse details of the rupture processes not only for the main events, but also for weaker seismicity preceding, accompanying and following the largest earthquakes. The seismic sequences accompanying recent large earthquakes showed several differences. In some cases, as for the 2014 Iquique earthquake, an important precursor activity took place in the months preceding the main shock, with an accelerating pattern in the last days before the main shock. In other cases, as for the recent Illapel earthquake, the main shock occurred with few precursors. The 2010 Maule earthquake showed an even different patterns, with the activation of secondary faults after the main shock. Recent studies were able to resolve significant changes in specific source parameters, such as changes in the distribution of focal mechanisms, potentially revealing a rotation of the stress tensor, or a spatial variation of rupture velocity, supporting a depth dependence of the rupture speed. An advanced inversion of seismic source parameters and their combined interpretation for multiple sequences can help to understand the diversity of rupture processes along the Chilean slab, and in general for subduction environments. We combine here results of different recent studies to investigate similarity and anomalies of rupture parameters for different seismic sequences, and foreshocks-aftershocks activities

  10. Aseismic and seismic slip induced by fluid injection from poroelastic and rate-state friction modeling

    Science.gov (United States)

    Liu, Y.; Deng, K.; Harrington, R. M.; Clerc, F.

    2016-12-01

    Solid matrix stress change and pore pressure diffusion caused by fluid injection has been postulated as key factors for inducing earthquakes and aseismic slip on pre-existing faults. In this study, we have developed a numerical model that simulates aseismic and seismic slip in a rate-and-state friction framework with poroelastic stress perturbations from multi-stage hydraulic fracturing scenarios. We apply the physics-based model to the 2013-2015 earthquake sequences near Fox Creek, Alberta, Canada, where three magnitude 4.5 earthquakes were potentially induced by nearby hydraulic fracturing activity. In particular, we use the relocated December 2013 seismicity sequence to approximate the fault orientation, and find the seismicity migration spatiotemporally correlate with the positive Coulomb stress changes calculated from the poroelastic model. When the poroelastic stress changes are introduced to the rate-state friction model, we find that slip on the fault evolves from aseismic to seismic in a manner similar to the onset of seismicity. For a 15-stage hydraulic fracturing that lasted for 10 days, modeled fault slip rate starts to accelerate after 3 days of fracking, and rapidly develops into a seismic event, which also temporally coincides with the onset of induced seismicity. The poroelastic stress perturbation and consequently fault slip rate continue to evolve and remain high for several weeks after hydraulic fracturing has stopped, which may explain the continued seismicity after shut-in. In a comparison numerical experiment, fault slip rate quickly decreases to the interseismic level when stress perturbations are instantaneously returned to zero at shut-in. Furthermore, when stress perturbations are removed just a few hours after the fault slip rate starts to accelerate (that is, hydraulic fracturing is shut down prematurely), only aseismic slip is observed in the model. Our preliminary results thus suggest the design of fracturing duration and flow

  11. Implementation of NGA-West2 ground motion models in the 2014 U.S. National Seismic Hazard Maps

    Science.gov (United States)

    Rezaeian, Sanaz; Petersen, Mark D.; Moschetti, Morgan P.; Powers, Peter; Harmsen, Stephen C.; Frankel, Arthur D.

    2014-01-01

    The U.S. National Seismic Hazard Maps (NSHMs) have been an important component of seismic design regulations in the United States for the past several decades. These maps present earthquake ground shaking intensities at specified probabilities of being exceeded over a 50-year time period. The previous version of the NSHMs was developed in 2008; during 2012 and 2013, scientists at the U.S. Geological Survey have been updating the maps based on their assessment of the “best available science,” resulting in the 2014 NSHMs. The update includes modifications to the seismic source models and the ground motion models (GMMs) for sites across the conterminous United States. This paper focuses on updates in the Western United States (WUS) due to the use of new GMMs for shallow crustal earthquakes in active tectonic regions developed by the Next Generation Attenuation (NGA-West2) project. Individual GMMs, their weighted combination, and their impact on the hazard maps relative to 2008 are discussed. In general, the combined effects of lower medians and increased standard deviations in the new GMMs have caused only small changes, within 5–20%, in the probabilistic ground motions for most sites across the WUS compared to the 2008 NSHMs.

  12. Using W-phase for regional source inversion: An application to the data from the virtual seismic network in the Western Pacific region

    Science.gov (United States)

    Liang, W.; Zhao, L.; Chen, P.; Yu, Y.; Liu, C.; Huang, B.; Kanamori, H.

    2009-12-01

    The W-phase inversion has been proven to be an efficient way to determine the magnitude and source mechanism of large earthquakes for tsunami warning purposes (Kanamori and Rivera, 2008). The Institute of Earth Sciences has exchanged seismic data in a real-time manner with other agencies in surrounding countries, including Japan, Vietnam, and Malaysia, to form a virtual seismic network in the western Pacific region. Any local organization may issue an earthquake report with its own data acquisition system individually. With the hypocentral information provided, we are able to apply this new technique to invert the data from this virtual regional network for the source mechanisms of large earthquakes which occurred on the major convergent plate boundary zones within 2-30 degrees. In this case, the W-phase will be completely retrieved in 1.5-12.5 minutes. To evaluate the reliability of inversion with this network geometry, we invert waveforms of scenario earthquakes synthesized by normal mode summation method. A series of examples were then studied to compare the difference between our results and the global CMT solutions. We hope this practical application will contribute to the tsunami mitigation and seismic hazard assessment in the Western Pacific and Southern Asia regions.

  13. Ultrasonic imaging of seismic physical models using a phase-shifted fiber Bragg grating.

    Science.gov (United States)

    Guo, Jingjing; Xue, Shigui; Zhao, Qun; Yang, Changxi

    2014-08-11

    We report what is to our knowledge the first ultrasonic imaging of seismic physical models by using a phase-shifted fiber Bragg grating (PS-FBG). Seismic models, which consist of multiple layer structures, were immersed in water. Piezoelectric (PZT) transducer was used to generate ultrasonic waves and a PS-FBG as a receiver. Two-dimensional (2D) ultrasonic images were reconstructed by scanning the PS-FBG with a high-precision position scanning device. In order to suppress the low-frequency drift of the Bragg wavelength during scanning, a tight wavelength tracking method was employed to lock the laser to the PS-FBG resonance in its reflection bandgap. The ultrasonic images captured by the PS-FBG have been compared with the images obtained by the geophysical imaging system, Sinopec, demonstrating the feasibility of our PS-FBG based imaging system in seismic modeling studies.

  14. Fast history matching of time-lapse seismic and production data for high resolution models

    Science.gov (United States)

    Jimenez Arismendi, Eduardo Antonio

    Integrated reservoir modeling has become an important part of day-to-day decision analysis in oil and gas management practices. A very attractive and promising technology is the use of time-lapse or 4D seismic as an essential component in subsurface modeling. Today, 4D seismic is enabling oil companies to optimize production and increase recovery through monitoring fluid movements throughout the reservoir. 4D seismic advances are also being driven by an increased need by the petroleum engineering community to become more quantitative and accurate in our ability to monitor reservoir processes. Qualitative interpretations of time-lapse anomalies are being replaced by quantitative inversions of 4D seismic data to produce accurate maps of fluid saturations, pore pressure, temperature, among others. Within all steps involved in this subsurface modeling process, the most demanding one is integrating the geologic model with dynamic field data, including 4Dseismic when available. The validation of the geologic model with observed dynamic data is accomplished through a "history matching" (HM) process typically carried out with well-based measurements. Due to low resolution of production data, the validation process is severely limited in its reservoir areal coverage, compromising the quality of the model and any subsequent predictive exercise. This research will aim to provide a novel history matching approach that can use information from high-resolution seismic data to supplement the areally sparse production data. The proposed approach will utilize streamline-derived sensitivities as means of relating the forward model performance with the prior geologic model. The essential ideas underlying this approach are similar to those used for high-frequency approximations in seismic wave propagation. In both cases, this leads to solutions that are defined along "streamlines" (fluid flow), or "rays" (seismic wave propagation). Synthetic and field data examples will be used

  15. Predictability in the Epidemic-Type Aftershock Sequence model of interacting triggered seismicity

    Science.gov (United States)

    Helmstetter, AgnèS.; Sornette, Didier

    2003-10-01

    As part of an effort to develop a systematic methodology for earthquake forecasting, we use a simple model of seismicity on the basis of interacting events which may trigger a cascade of earthquakes, known as the Epidemic-Type Aftershock Sequence model (ETAS). The ETAS model is constructed on a bare (unrenormalized) Omori law, the Gutenberg-Richter law, and the idea that large events trigger more numerous aftershocks. For simplicity, we do not use the information on the spatial location of earthquakes and work only in the time domain. We demonstrate the essential role played by the cascade of triggered seismicity in controlling the rate of aftershock decay as well as the overall level of seismicity in the presence of a constant external seismicity source. We offer an analytical approach to account for the yet unobserved triggered seismicity adapted to the problem of forecasting future seismic rates at varying horizons from the present. Tests presented on synthetic catalogs validate strongly the importance of taking into account all the cascades of still unobserved triggered events in order to predict correctly the future level of seismicity beyond a few minutes. We find a strong predictability if one accepts to predict only a small fraction of the large-magnitude targets. Specifically, we find a prediction gain (defined as the ratio of the fraction of predicted events over the fraction of time in alarms) equal to 21 for a fraction of alarm of 1%, a target magnitude M ≥ 6, an update time of 0.5 days between two predictions, and for realistic parameters of the ETAS model. However, the probability gains degrade fast when one attempts to predict a larger fraction of the targets. This is because a significant fraction of events remain uncorrelated from past seismicity. This delineates the fundamental limits underlying forecasting skills, stemming from an intrinsic stochastic component in these interacting triggered seismicity models. Quantitatively, the fundamental

  16. THMC Modeling of EGS Reservoirs -- Continuum through Discontinuum Representations. Capturing Reservoir Stimulation, Evolution and Induced Seismicity

    Energy Technology Data Exchange (ETDEWEB)

    Elsworth, Derek [Pennsylvania State Univ., State College, PA (United States); Izadi, Ghazal [Pennsylvania State Univ., State College, PA (United States); Gan, Quan [Pennsylvania State Univ., State College, PA (United States); Fang, Yi [Pennsylvania State Univ., State College, PA (United States); Taron, Josh [US Geological Survey, Menlo Park, CA (United States); Sonnenthal, Eric [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-07-28

    This work has investigated the roles of effective stress induced by changes in fluid pressure, temperature and chemistry in contributing to the evolution of permeability and induced seismicity in geothermal reservoirs. This work has developed continuum models [1] to represent the progress or seismicity during both stimulation [2] and production [3]. These methods have been used to resolve anomalous observations of induced seismicity at the Newberry Volcano demonstration project [4] through the application of modeling and experimentation. Later work then focuses on the occurrence of late stage seismicity induced by thermal stresses [5] including the codifying of the timing and severity of such responses [6]. Furthermore, mechanistic linkages between observed seismicity and the evolution of permeability have been developed using data from the Newberry project [7] and benchmarked against field injection experiments. Finally, discontinuum models [8] incorporating the roles of discrete fracture networks have been applied to represent stimulation and then thermal recovery for new arrangements of geothermal wells incorporating the development of flow manifolds [9] in order to increase thermal output and longevity in EGS systems.

  17. A Contribution to Mitigating Seismic Risk in the Bay Area: The Bay Area Regional Deformation (BARD) GPS Network

    Science.gov (United States)

    Houlie, N.; Romanowicz, B.; Hellweg, P.

    2007-05-01

    In the San Francisco Bay Area (SFBA), two million people live in a geologically complex, tectonically active region that has experienced several historic earthquakes, including the 1868 Hayward, the 1906 San Francisco, and 1989 Loma Prieta earthquakes. Geodetic measurements, which are especially useful for detecting deformation and strain on deep structures throughout the seismic cycle, show that Bay Area deformation is both spatially complex and varying with time. Increasingly, GPS data can also be used in real time to complement seismic data in providing robust real-time earthquake information, and, potentially, early warning. The Bay Area Regional Deformation (BARD) network of permanent, continuously operating Global Positioning System (GPS) receivers monitors crustal deformation in the Bay Area and northern California. BARD is a network collocated with several seismic networks (BDSN, NHFN, mini-PBO) operating in Northern California. As the local determination of magnitude is problematic for large earthquakes, the GPS will provide strong constraints on rupture geometry and amount of slip along the slipping fault. Thus, the collocation of all the networks will help mitigate earthquake- related risks associated with an earthquake in the SFBA or in northern California.

  18. A way to synchronize models with seismic faults for earthquake forecasting

    DEFF Research Database (Denmark)

    González, Á.; Gómez, J.B.; Vázquez-Prada, M.

    2006-01-01

    Numerical models are starting to be used for determining the future behaviour of seismic faults and fault networks. Their final goal would be to forecast future large earthquakes. In order to use them for this task, it is necessary to synchronize each model with the current status of the actual f...

  19. 3-D imaging of seismic data from a physical model of a salt structure

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, P. M. (Peter M.); Huang, L. (Lianjie); House, L. S. (Leigh S.); Wiley, R. (Robert)

    2001-01-01

    Seismic data from a physical model of the SEG/EAGE salt structure were imaged to evaluate the quality of imaging of a complex structure and benchmark imaging codes. The physical model was constructed at the University of Houston. Two simulated marine surveys were collected from it: a conventional towed streamer survey, and a vertical receiver cable survey.

  20. Viscoplastic discontinuum model of time-dependent fracture and seismicity effects in brittle rock

    CSIR Research Space (South Africa)

    Napier, JAL

    1997-10-01

    Full Text Available A model is proposed for the direct mechanistic simulation of seismic activity and stress transfer effects in deep level mines. The model uses a discontinuum viscoplastic formulation to relate the rate of slip on a crack to the shear stress acting...

  1. Focal Depth of the WenChuan Earthquake Aftershocks from modeling of Seismic Depth Phases

    Science.gov (United States)

    Luo, Y.; Zeng, X.; Chong, J.; Ni, S.; Chen, Y.

    2008-12-01

    After the 05/12/2008 great WenChuan earthquake in Sichuan Province of China, tens of thousands earthquakes occurred with hundreds of them stronger than M4. Those aftershocks provide valuable information about seismotectonics and rupture processes for the mainshock, particularly accurate spatial distribution of aftershocks is very informational for determining rupture fault planes. However focal depth can not be well resolved just with first arrivals recorded by relatively sparse network in Sichuan Province, therefore 3D seismicity distribution is difficult to obtain though horizontal location can be located with accuracy of 5km. Instead local/regional depth phases such as sPmP, sPn, sPL and teleseismic pP,sP are very sensitive to depth, and be readily modeled to determine depth with accuracy of 2km. With reference 1D velocity structure resolved from receiver functions and seismic refraction studies, local/regional depth phases such as sPmP, sPn and sPL are identified by comparing observed waveform with synthetic seismograms by generalized ray theory and reflectivity methods. For teleseismic depth phases well observed for M5.5 and stronger events, we developed an algorithm in inverting both depth and focal mechanism from P and SH waveforms. Also we employed the Cut and Paste (CAP) method developed by Zhao and Helmberger in modeling mechanism and depth with local waveforms, which constrains depth by fitting Pnl waveforms and the relative weight between surface wave and Pnl. After modeling all the depth phases for hundreds of events , we find that most of the M4 earthquakes occur between 2-18km depth, with aftershocks depth ranging 4-12km in the southern half of Longmenshan fault while aftershocks in the northern half featuring large depth range up to 18km. Therefore seismogenic zone in the northern segment is deeper as compared to the southern segment. All the aftershocks occur in upper crust, given that the Moho is deeper than 40km, or even 60km west of the

  2. Study of Gutenberg-Richter coefficients considering time evolution for different mexican seismic regions

    Science.gov (United States)

    Carrizales Velazquez, Carlos; Angulo Brown, Fernando

    2017-04-01

    In the present work, we propose a division of the Mexican Pacific coast and we study the time evolution of the Gutenberg-Richter coefficients ("a" and "b" values) along the 2006-2016 period by means of the sliding time window method. We observed that the sequences of a and b values obtained, are positively correlated as it must be, because otherwise it would represent a seismic dynamics incompatible with a self-organized critical system "the earth crust". Furthermore, we analyze the variation of the modal value "a/b" showing be a better estimator of seismic activity that only a or b parameters. Finally, we perform size window variation analysis to keep constant the seismic energy released by N-events into the time window.

  3. A Vs30-derived Near-surface Seismic Velocity Model

    Science.gov (United States)

    Ely, G. P.; Jordan, T. H.; Small, P.; Maechling, P. J.

    2010-12-01

    Shallow material properties, S-wave velocity in particular, strongly influence ground motions, so must be accurately characterized for ground-motion simulations. Available near-surface velocity information generally exceeds that which is accommodated by crustal velocity models, such as current versions of the SCEC Community Velocity Model (CVM-S4) or the Harvard model (CVM-H6). The elevation-referenced CVM-H voxel model introduces rasterization artifacts in the near-surface due to course sample spacing, and sample depth dependence on local topographic elevation. To address these issues, we propose a method to supplement crustal velocity models, in the upper few hundred meters, with a model derived from available maps of Vs30 (the average S-wave velocity down to 30 meters). The method is universally applicable to regions without direct measures of Vs30 by using Vs30 estimates from topographic slope (Wald, et al. 2007). In our current implementation for Southern California, the geology-based Vs30 map of Wills and Clahan (2006) is used within California, and topography-estimated Vs30 is used outside of California. Various formulations for S-wave velocity depth dependence, such as linear spline and polynomial interpolation, are evaluated against the following priorities: (a) capability to represent a wide range of soil and rock velocity profile types; (b) smooth transition to the crustal velocity model; (c) ability to reasonably handle poor spatial correlation of Vs30 and crustal velocity data; (d) simplicity and minimal parameterization; and (e) computational efficiency. The favored model includes cubic and square-root depth dependence, with the model extending to a depth of 350 meters. Model parameters are fit to Boore and Joyner's (1997) generic rock profile as well as CVM-4 soil profiles for the NEHRP soil classification types. P-wave velocity and density are derived from S-wave velocity by the scaling laws of Brocher (2005). Preliminary assessment of the new model

  4. A unified classification model for modeling of seismic liquefaction potential of soil based on CPT.

    Science.gov (United States)

    Samui, Pijush; Hariharan, R

    2015-07-01

    The evaluation of liquefaction potential of soil due to an earthquake is an important step in geosciences. This article examines the capability of Minimax Probability Machine (MPM) for the prediction of seismic liquefaction potential of soil based on the Cone Penetration Test (CPT) data. The dataset has been taken from Chi-Chi earthquake. MPM is developed based on the use of hyperplanes. It has been adopted as a classification tool. This article uses two models (MODEL I and MODEL II). MODEL I employs Cone Resistance (q c) and Cyclic Stress Ratio (CSR) as input variables. q c and Peak Ground Acceleration (PGA) have been taken as inputs for MODEL II. The developed MPM gives 100% accuracy. The results show that the developed MPM can predict liquefaction potential of soil based on q c and PGA.

  5. Subduction and interplate seismicity: new insights from statistical analysis of natural data and analog-numerical modeling

    Science.gov (United States)

    Funiciello, F.; Corbi, F.; Heuret, A.; van Dinther, Y.; Presti, D.; Marzocchi, W.; Sandri, L.; Moroni, M.; Gerya, T.; Mai, P. M.; Dalguer, L. A.; Lallemand, S.; Piromallo, C.; Conrad, C. P.; Faccenna, C.; Seismological Section Of The Euryi (European Young Investigator Award) Team

    2011-12-01

    Subduction zones are the site of the largest and most dangerous seismic events occurring on the Earth. The interface of converging plates is comprised of major fault zones where most of the total seismic moment is released due to the global seismicity. Despite first order similarities between convergent margins, the statistical distribution of interplate seismic activity on different subduction zones is considerably diverse: some regions are characterized by the occurrence of megathrust earthquakes while others show only minor seismic activity, with moderate-sized events. Determining the causes of this variability is challenging. While essential features characterizing the behavior of the subduction thrust faults are known, it is still difficult to merge them in a single, comprehensive picture. This is mainly related to the lack of direct observables (i.e. subduction thrust faults are not readily accessible developing in the deeper crust, in the offshore domain) and to a short (i.e. limited to the last century) instrumental seismic record. Here we present the main results of an interdisciplinary study realized in the framework of the ESF (European Science Foundation) - EURYI project 'Convergent margins and seismogenesis: defining the risk of great earthquakes by using statistical data and modeling'. This project aims to improve the current understanding of the physics of subduction zone thrust fault earthquakes, analyzing and gathering a) a wide range of geometric, kinematic and seismological data on current subduction zones and related statistical analysis and b) results of innovative laboratory and numerical models. In particular, our results allow us to identify many interesting features characterizing interplate earthquakes, for example; 1) the key role played by the velocity of subduction in defining both the geometry and the mechanical behavior of the subduction thrust fault; 2) the competing role played by size and distribution of protrusions of the plate

  6. Automatic detection of avalanches in seismic data using Hidden Markov Models

    Science.gov (United States)

    Heck, Matthias; Hammer, Conny; van Herwijnen, Alec; Schweizer, Jürg; Fäh, Donat

    2017-04-01

    Seismic monitoring systems are well suited for the remote detection of mass movements, such as landslides, rockfalls and debris flows. For snow avalanches, this has been known since the 1970s and seismic monitoring could potentially provide valuable information for avalanche forecasting. We thus explored continuous seismic data from a string of vertical component geophones in an avalanche starting zone above Davos, Switzerland. The overall goal is to automatically detect avalanches with a Hidden Markov Model (HMM), a statistical pattern recognition tool widely used for speech recognition. A HMM uses a classifier to determine the likelihood that input objects belong to a finite number of classes. These classes are obtained by learning a multidimensional Gaussian mixture model representation of the overall observable feature space. This model is then used to derive the HMM parameters for avalanche waveforms using a single training sample to build the final classifier. We classified data from the winter seasons of 2010 and compared the results to several hundred avalanches manually identified in the seismic data. First results of a classification of a single day have shown, that the model is good in terms of probability of detection while having a relatively low false alarm rate. We further implemented a voting based classification approach to neglect events detected only by one sensor to further improve the model performance. For instance, on 22 March 2010, a day with particular high avalanche activity, 17 avalanches were positively identified by at least three sensors with no false alarms. These results show, that the automatic detection of avalanches in seismic data is feasible, bringing us one step closer to implementing seismic monitoring system in operational forecasting.

  7. Seismic Structure of Southern African Cratons

    DEFF Research Database (Denmark)

    Soliman, Mohammad Youssof Ahmad; Artemieva, Irina; Levander, Alan

    2014-01-01

    Cratons are extremely stable continental crustal areas above thick depleted lithosphere. These regions have remained largely unchanged for more than 2.5 Ga. This study presents a new seismic model of the seismic structure of the crust and lithospheric mantle constrained by seismic receiver...... functions and finite-frequency tomography based on data from the South Africa Seismic Experiment (SASE). Combining the two methods provides high vertical and lateral resolution. The main results obtained are (1) the presence of a highly heterogeneous crustal structure, in terms of thickness, composition (as...

  8. Evidencing a prominent Moho topography beneath the Iberian-Western Mediterranean Region, compiled from controlled-source and natural seismic surveys

    Science.gov (United States)

    Diaz, Jordi; Gallart, Josep; Carbonell, Ramon

    2016-04-01

    The complex tectonic interaction processes between the European and African plates at the Western Mediterranean since Mesozoic times have left marked imprints in the present-day crustal architecture of this area, particularly as regarding the lateral variations in crustal and lithospheric thicknesses. The detailed mapping of such variations is essential to understand the regional geodynamics, as it provides major constraints for different seismological, geophysical and geodynamic modeling methods both at lithospheric and asthenospheric scales. Since the 1970s, the lithospheric structure beneath the Iberian Peninsula and its continental margins has been extensively investigated using deep multichannel seismic reflection and refraction/wide-angle reflection profiling experiments. Diaz and Gallart (2009) presented a compilation of the results then available beneath the Iberian Peninsula. In order to improve the picture of the whole region, we have now extended the geographical area to include northern Morocco and surrounding waters. We have also included in the compilation the results arising from all the seismic surveys performed in the area and documented in the last few years. The availability of broad-band sensors and data-loggers equipped with large storage capabilities has allowed in the last decade to boost the investigations on crustal and lithospheric structure using natural seismicity, providing a spatial resolution never achieved before. The TopoIberia-Iberarray network, deployed over Iberia and northern Morocco, has provided a good example of those new generation seismic experiments. The data base holds ~300 sites, including the permanent networks in the area and hence forming a unique seismic database in Europe. In this contribution, we retrieve the results on crustal thickness presented by Mancilla and Diaz (2015) using data from the TopoIberia and associated experiments and we complement them with additional estimations beneath the Rif Cordillera

  9. Necessity of using heterogeneous ellipsoidal Earth model with terrain to calculate co-seismic effect

    Science.gov (United States)

    Cheng, Huihong; Zhang, Bei; Zhang, Huai; Huang, Luyuan; Qu, Wulin; Shi, Yaolin

    2016-04-01

    Co-seismic deformation and stress changes, which reflect the elasticity of the earth, are very important in the earthquake dynamics, and also to other issues, such as the evaluation of the seismic risk, fracture process and triggering of earthquake. Lots of scholars have researched the dislocation theory and co-seismic deformation and obtained the half-space homogeneous model, half-space stratified model, spherical stratified model, and so on. Especially, models of Okada (1992) and Wang (2003, 2006) are widely applied in the research of calculating co-seismic and post-seismic effects. However, since both semi-infinite space model and layered model do not take the role of the earth curvature or heterogeneity or topography into consideration, there are large errors in calculating the co-seismic displacement of a great earthquake in its impacted area. Meanwhile, the computational methods of calculating the co-seismic strain and stress are different between spherical model and plane model. Here, we adopted the finite element method which could well deal with the complex characteristics (such as anisotropy, discontinuities) of rock and different conditions. We use the mash adaptive technique to automatically encrypt the mesh at the fault and adopt the equivalent volume force replace the dislocation source, which can avoid the difficulty in handling discontinuity surface with conventional (Zhang et al., 2015). We constructed an earth model that included earth's layered structure and curvature, the upper boundary was set as a free surface and the core-mantle boundary was set under buoyancy forces. Firstly, based on the precision requirement, we take a testing model - - a strike-slip fault (the length of fault is 500km and the width is 50km, and the slippage is 10m) for example. Because of the curvature of the Earth, some errors certainly occur in plane coordinates just as previous studies (Dong et al., 2014; Sun et al., 2012). However, we also found that: 1) the co-seismic

  10. A Short Term Seismic Hazard Assessment in Christchurch, New Zealand, After the M 7.1, 4 September 2010 Darfield Earthquake: An Application of a Smoothing Kernel and Rate-and-State Friction Model

    Directory of Open Access Journals (Sweden)

    Chung-Han Chan

    2012-01-01

    Full Text Available The Mw 6.3, 21 February 2011 Christchurch, New Zealand, earthquake is regarded as an aftershock of the M 7.1, 4 September 2010 Darfield earthquake. However, it caused severe damage in the downtown Christchurch. Such a circumstance points out the importance of an aftershock sequence in seismic hazard evaluation and suggests the re-evaluation of a seismic hazard immediately after a large earthquake occurrence. For this purpose, we propose a probabilistic seismic hazard assessment (PSHA, which takes the disturbance of a short-term seismicity rate into account and can be easily applied in comparison with the classical PSHA. In our approach, the treatment of the background seismicity rate is the same as in the zoneless approach, which considers a bandwidth function as a smoothing Kernel in neighboring region of earthquakes. The rate-and-state friction model imparted by the Coulomb stress change